src/Compilers/CSharp/Test/Emit3/Semantics/OutVarTests.cs - main - githubmirror/roslyn

src/Compilers/CSharp/Test/Emit3/Semantics/OutVarTests.cs
36 570 строк1 MB
Stephan Bauer
Add separate error for disallowed members in global namespace (#81221)
18 дек 2025, 19:48
18 дек 2025, 19:4843bebc0
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

#nullable disable

using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using Basic.Reference.Assemblies;
using Microsoft.CodeAnalysis.Collections;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Test.Utilities;
using Roslyn.Test.Utilities;
using Roslyn.Utilities;
using Xunit;

namespace Microsoft.CodeAnalysis.CSharp.UnitTests
{
    [CompilerTrait(CompilerFeature.OutVar)]
    public class OutVarTests : CompilingTestBase
    {

        [Fact]
        public void OldVersion()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int x1), x1);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, int y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular.WithLanguageVersion(LanguageVersion.CSharp6));
            compilation.VerifyDiagnostics(
                // (6,21): error CS8059: Feature 'out variable declaration' is not available in C# 6. Please use language version 7.0 or greater.
                //         Test2(Test1(out int x1), x1);
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion6, "out").WithArguments("out variable declaration", "7.0").WithLocation(6, 21));

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        [WorkItem(12182, "https://github.com/dotnet/roslyn/issues/12182")]
        [WorkItem(16348, "https://github.com/dotnet/roslyn/issues/16348")]
        public void DiagnosticsDifferenceBetweenLanguageVersions_01()
        {
            var text = @"
public class Cls
{
    public static void Test1()
    {
        Test(out int x1);
    }

    public static void Test2()
    {
        var x = new Cls(out int x2);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular.WithLanguageVersion(LanguageVersion.CSharp6));
            compilation.VerifyDiagnostics(
                // (6,9): error CS0103: The name 'Test' does not exist in the current context
                //         Test(out int x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "Test").WithArguments("Test").WithLocation(6, 9),
                // (6,14): error CS8059: Feature 'out variable declaration' is not available in C# 6. Please use language version 7.0 or greater.
                //         Test(out int x1);
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion6, "out").WithArguments("out variable declaration", "7.0").WithLocation(6, 14),
                // (11,25): error CS8059: Feature 'out variable declaration' is not available in C# 6. Please use language version 7.0 or greater.
                //         var x = new Cls(out int x2);
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion6, "out").WithArguments("out variable declaration", "7.0").WithLocation(11, 25),
                // (11,21): error CS1729: 'Cls' does not contain a constructor that takes 1 arguments
                //         var x = new Cls(out int x2);
                Diagnostic(ErrorCode.ERR_BadCtorArgCount, "Cls").WithArguments("Cls", "1").WithLocation(11, 21),
                // (11,29): error CS0165: Use of unassigned local variable 'x2'
                //         var x = new Cls(out int x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "int x2").WithArguments("x2").WithLocation(11, 29));

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);

            var x2Decl = GetOutVarDeclaration(tree, "x2");
            //VerifyModelForOutVar(model, x2Decl); Probably fails due to https://github.com/dotnet/roslyn/issues/16348
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl);

            compilation = CreateCompilation(text, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (6,9): error CS0103: The name 'Test' does not exist in the current context
                //         Test(out int x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "Test").WithArguments("Test").WithLocation(6, 9),
                // (11,21): error CS1729: 'Cls' does not contain a constructor that takes 1 arguments
                //         var x = new Cls(out int x2);
                Diagnostic(ErrorCode.ERR_BadCtorArgCount, "Cls").WithArguments("Cls", "1").WithLocation(11, 21),
                // (11,29): error CS0165: Use of unassigned local variable 'x2'
                //         var x = new Cls(out int x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "int x2").WithArguments("x2").WithLocation(11, 29)
                );

            tree = compilation.SyntaxTrees.Single();
            model = compilation.GetSemanticModel(tree);

            x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);

            x2Decl = GetOutVarDeclaration(tree, "x2");
            //VerifyModelForOutVar(model, x2Decl); Probably fails due to https://github.com/dotnet/roslyn/issues/16348
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out var (x1, x2));
        System.Console.WriteLine(x1);
        System.Console.WriteLine(x2);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1, x2)").WithLocation(6, 19),
                // (6,24): error CS0103: The name 'x1' does not exist in the current context
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(6, 24),
                // (6,28): error CS0103: The name 'x2' does not exist in the current context
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x2").WithArguments("x2").WithLocation(6, 28),
                // (6,19): error CS0103: The name 'var' does not exist in the current context
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(6, 19),
                // (7,34): error CS0103: The name 'x1' does not exist in the current context
                //         System.Console.WriteLine(x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(7, 34),
                // (8,34): error CS0103: The name 'x2' does not exist in the current context
                //         System.Console.WriteLine(x2);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x2").WithArguments("x2").WithLocation(8, 34)
                );

            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out (var x1, var x2));
        System.Console.WriteLine(x1);
        System.Console.WriteLine(x2);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilationWithMscorlib40(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,20): error CS8185: A declaration is not allowed in this context.
                //         Test1(out (var x1, var x2));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "var x1").WithLocation(6, 20),
                // (6,28): error CS8185: A declaration is not allowed in this context.
                //         Test1(out (var x1, var x2));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "var x2").WithLocation(6, 28),
                // (6,19): error CS8179: Predefined type 'System.ValueTuple`2' is not defined or imported
                //         Test1(out (var x1, var x2));
                Diagnostic(ErrorCode.ERR_PredefinedValueTupleTypeNotFound, "(var x1, var x2)").WithArguments("System.ValueTuple`2").WithLocation(6, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetDeclaration(tree, "x2");
            var x2Ref = GetReference(tree, "x2");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x2Decl, x2Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out (int x1, long x2));
        System.Console.WriteLine(x1);
        System.Console.WriteLine(x2);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilationWithMscorlib40(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,20): error CS8185: A declaration is not allowed in this context.
                //         Test1(out (int x1, long x2));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "int x1").WithLocation(6, 20),
                // (6,28): error CS8185: A declaration is not allowed in this context.
                //         Test1(out (int x1, long x2));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "long x2").WithLocation(6, 28),
                // (6,19): error CS8179: Predefined type 'System.ValueTuple`2' is not defined or imported
                //         Test1(out (int x1, long x2));
                Diagnostic(ErrorCode.ERR_PredefinedValueTupleTypeNotFound, "(int x1, long x2)").WithArguments("System.ValueTuple`2").WithLocation(6, 19),
                // (6,20): error CS0165: Use of unassigned local variable 'x1'
                //         Test1(out (int x1, long x2));
                Diagnostic(ErrorCode.ERR_UseDefViolation, "int x1").WithArguments("x1").WithLocation(6, 20),
                // (6,28): error CS0165: Use of unassigned local variable 'x2'
                //         Test1(out (int x1, long x2));
                Diagnostic(ErrorCode.ERR_UseDefViolation, "long x2").WithArguments("x2").WithLocation(6, 28)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetDeclaration(tree, "x2");
            var x2Ref = GetReference(tree, "x2");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x2Decl, x2Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_04()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out (int x1, (long x2, byte x3)));
        System.Console.WriteLine(x1);
        System.Console.WriteLine(x2);
        System.Console.WriteLine(x3);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilationWithMscorlib40(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,20): error CS8185: A declaration is not allowed in this context.
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "int x1").WithLocation(6, 20),
                // (6,29): error CS8185: A declaration is not allowed in this context.
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "long x2").WithLocation(6, 29),
                // (6,38): error CS8185: A declaration is not allowed in this context.
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "byte x3").WithLocation(6, 38),
                // (6,28): error CS8179: Predefined type 'System.ValueTuple`2' is not defined or imported
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_PredefinedValueTupleTypeNotFound, "(long x2, byte x3)").WithArguments("System.ValueTuple`2").WithLocation(6, 28),
                // (6,19): error CS8179: Predefined type 'System.ValueTuple`2' is not defined or imported
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_PredefinedValueTupleTypeNotFound, "(int x1, (long x2, byte x3))").WithArguments("System.ValueTuple`2").WithLocation(6, 19),
                // (6,20): error CS0165: Use of unassigned local variable 'x1'
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_UseDefViolation, "int x1").WithArguments("x1").WithLocation(6, 20),
                // (6,29): error CS0165: Use of unassigned local variable 'x2'
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_UseDefViolation, "long x2").WithArguments("x2").WithLocation(6, 29),
                // (6,38): error CS0165: Use of unassigned local variable 'x3'
                //         Test1(out (int x1, (long x2, byte x3)));
                Diagnostic(ErrorCode.ERR_UseDefViolation, "byte x3").WithArguments("x3").WithLocation(6, 38)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetDeclaration(tree, "x2");
            var x2Ref = GetReference(tree, "x2");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x2Decl, x2Ref);

            var x3Decl = GetDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x3Decl, x3Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_05()
        {
            var text = @"
public class Cls
{
    private static int F1;

    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        object x3 = null;
        Test1(out var (x1, (x2, x3)));
        System.Console.WriteLine(F1);
    }

    static ref int var(object x, object y)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (11,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (x1, (x2, x3)));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1, (x2, x3))").WithLocation(11, 19)
                );

            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_06()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        Test1(out var (x1));
        System.Console.WriteLine(F1);
    }

    static ref int var(object x)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (8,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (x1));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1)").WithLocation(8, 19)
                );
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_07()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        Test1(out var (x1, x2: x2));
        System.Console.WriteLine(F1);
    }

    static ref int var(object x1, object x2)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (x1, x2: x2));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1, x2: x2)").WithLocation(9, 19)
                );
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_08()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        Test1(out var (ref x1, x2));
        System.Console.WriteLine(F1);
    }

    static ref int var(ref object x1, object x2)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (ref x1, x2));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (ref x1, x2)").WithLocation(9, 19)
                );
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_09()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        Test1(out var (x1, (x2)));
        System.Console.WriteLine(F1);
    }

    static ref int var(object x1, object x2)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (x1, (x2)));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1, (x2))").WithLocation(9, 19)
                );
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_10()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        Test1(out var ((x1), x2));
        System.Console.WriteLine(F1);
    }

    static ref int var(object x1, object x2)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var ((x1), x2));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var ((x1), x2)").WithLocation(9, 19)
                );
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_11()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out var (x1, x2));
        System.Console.WriteLine(x1);
        System.Console.WriteLine(x2);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular.WithLanguageVersion(LanguageVersion.CSharp6));

            compilation.VerifyDiagnostics(
                // (6,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1, x2)").WithLocation(6, 19),
                // (6,24): error CS0103: The name 'x1' does not exist in the current context
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(6, 24),
                // (6,28): error CS0103: The name 'x2' does not exist in the current context
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x2").WithArguments("x2").WithLocation(6, 28),
                // (6,19): error CS0103: The name 'var' does not exist in the current context
                //         Test1(out var (x1, x2));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(6, 19),
                // (7,34): error CS0103: The name 'x1' does not exist in the current context
                //         System.Console.WriteLine(x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(7, 34),
                // (8,34): error CS0103: The name 'x2' does not exist in the current context
                //         System.Console.WriteLine(x2);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x2").WithArguments("x2").WithLocation(8, 34)
                );

            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_12()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        Test1(out M1 (x1, x2));
        System.Console.WriteLine(F1);
    }

    static ref int M1(object x1, object x2)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics();

            CompileAndVerify(compilation, expectedOutput: "123");
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_13()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        Test1(ref var (x1, x2));
        System.Console.WriteLine(F1);
    }

    static ref int var(object x1, object x2)
    {
        return ref F1;
    }

    static object Test1(ref int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(ref var (x1, x2));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1, x2)").WithLocation(9, 19)
                );
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_14()
        {
            var text = @"
public class Cls
{
    private static int F1;
    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        Test1(var (x1, x2));
        System.Console.WriteLine(F1);
    }

    static int var(object x1, object x2)
    {
        F1 = 123;
        return 124;
    }

    static object Test1(int x)
    {
        System.Console.WriteLine(x);
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics();

            CompileAndVerify(compilation, expectedOutput:
@"124
123");

            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_15()
        {
            var text = @"
public class Cls
{
    private static int F1;

    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        object x3 = null;
        Test1(out M1 (x1, (x2, x3)));
        System.Console.WriteLine(F1);
    }

    static ref int M1(object x, object y)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics();

            CompileAndVerify(compilation, expectedOutput: "123");
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        [WorkItem(13148, "https://github.com/dotnet/roslyn/issues/13148")]
        public void OutVarDeconstruction_16()
        {
            var text = @"
public class Cls
{
    private static int F1;

    public static void Main()
    {
        object x1 = null;
        object x2 = null;
        object x3 = null;
        Test1(out var (x1, (a: x2, b: x3)));
        System.Console.WriteLine(F1);
    }

    static ref int var(object x, object y)
    {
        return ref F1;
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (11,19): error CS8199: The syntax 'var (...)' as an lvalue is reserved.
                //         Test1(out var (x1, (a: x2, b: x3)));
                Diagnostic(ErrorCode.ERR_VarInvocationLvalueReserved, "var (x1, (a: x2, b: x3))").WithLocation(11, 19)
                );
            Assert.False(compilation.SyntaxTrees.Single().GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>().Any());
        }

        private static IdentifierNameSyntax GetReference(SyntaxTree tree, string name)
        {
            return GetReferences(tree, name).Single();
        }

        private static IdentifierNameSyntax[] GetReferences(SyntaxTree tree, string name, int count)
        {
            var nameRef = GetReferences(tree, name).ToArray();
            Assert.Equal(count, nameRef.Length);
            return nameRef;
        }

        internal static IEnumerable<IdentifierNameSyntax> GetReferences(SyntaxTree tree, string name)
        {
            return tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == name);
        }

        private static IEnumerable<DeclarationExpressionSyntax> GetDeclarations(SyntaxTree tree, string name)
        {
            return tree.GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>()
                    .Where(p => p.Identifier().ValueText == name);
        }

        private static DeclarationExpressionSyntax GetDeclaration(SyntaxTree tree, string name)
        {
            return GetDeclarations(tree, name).Single();
        }

        internal static DeclarationExpressionSyntax GetOutVarDeclaration(SyntaxTree tree, string name)
        {
            return GetOutVarDeclarations(tree, name).Single();
        }

        private static IEnumerable<DeclarationExpressionSyntax> GetOutVarDeclarations(SyntaxTree tree, string name)
        {
            return tree.GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>()
                    .Where(p => p.IsOutVarDeclaration() && p.Identifier().ValueText == name);
        }

        private static IEnumerable<DiscardDesignationSyntax> GetDiscardDesignations(SyntaxTree tree)
        {
            return tree.GetRoot().DescendantNodes().OfType<DiscardDesignationSyntax>();
        }

        private static IEnumerable<IdentifierNameSyntax> GetDiscardIdentifiers(SyntaxTree tree)
        {
            return tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(i => i.Identifier.ContextualKind() == SyntaxKind.UnderscoreToken);
        }

        private static IEnumerable<DeclarationExpressionSyntax> GetOutVarDeclarations(SyntaxTree tree)
        {
            return tree.GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>()
                    .Where(p => p.IsOutVarDeclaration());
        }

        [Fact]
        public void Simple_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int x1), x1);
        int x2;
        Test3(out x2);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, int y)
    {
        System.Console.WriteLine(y);
    }

    static void Test3(out int y)
    {
        y = 0;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Ref = GetReference(tree, "x2");
            Assert.Null(model.GetDeclaredSymbol(x2Ref));
            Assert.Null(model.GetDeclaredSymbol((ArgumentSyntax)x2Ref.Parent));
        }

        private static void VerifyModelForOutVarWithoutDataFlow(SemanticModel model, DeclarationExpressionSyntax decl, params IdentifierNameSyntax[] references)
        {
            VerifyModelForOutVarWithoutDataFlow(model, decl, isShadowed: false, references: references);
        }

        private static void VerifyModelForOutVarWithoutDataFlow(SemanticModel model, DeclarationExpressionSyntax decl, bool isShadowed, params IdentifierNameSyntax[] references)
        {
            VerifyModelForOutVar(model, decl, isDelegateCreation: false, isExecutableCode: true, isShadowed: isShadowed, verifyDataFlow: false, references: references);
        }

        private static void VerifyModelForDeclarationVarWithoutDataFlow(SemanticModel model, DeclarationExpressionSyntax decl, params IdentifierNameSyntax[] references)
        {
            VerifyModelForOutVar(model, decl, isDelegateCreation: false, isExecutableCode: true, isShadowed: false, verifyDataFlow: false, expectedLocalKind: LocalDeclarationKind.DeclarationExpressionVariable, references: references);
        }

        internal static void VerifyModelForOutVar(SemanticModel model, DeclarationExpressionSyntax decl, params IdentifierNameSyntax[] references)
        {
            VerifyModelForOutVar(model, decl, isDelegateCreation: false, isExecutableCode: true, isShadowed: false, verifyDataFlow: true, references: references);
        }

        private static void VerifyModelForOutVarInNotExecutableCode(SemanticModel model, DeclarationExpressionSyntax decl, params IdentifierNameSyntax[] references)
        {
            VerifyModelForOutVar(model, decl, isDelegateCreation: false, isExecutableCode: false, isShadowed: false, verifyDataFlow: true, references: references);
        }

        private static void VerifyModelForOutVarInNotExecutableCode(
            SemanticModel model,
            DeclarationExpressionSyntax decl,
            IdentifierNameSyntax reference)
        {
            VerifyModelForOutVar(
                model, decl, isDelegateCreation: false, isExecutableCode: false, isShadowed: false,
                verifyDataFlow: true, references: reference);
        }

        private static void VerifyModelForOutVar(
            SemanticModel model,
            DeclarationExpressionSyntax decl,
            bool isDelegateCreation,
            bool isExecutableCode,
            bool isShadowed,
            bool verifyDataFlow = true,
            LocalDeclarationKind expectedLocalKind = LocalDeclarationKind.OutVariable,
            params IdentifierNameSyntax[] references)
        {
            var variableDeclaratorSyntax = GetVariableDesignation(decl);
            var symbol = model.GetDeclaredSymbol(variableDeclaratorSyntax);
            Assert.NotNull(symbol);
            Assert.Equal(decl.Identifier().ValueText, symbol.Name);
            Assert.Equal(variableDeclaratorSyntax, symbol.DeclaringSyntaxReferences.Single().GetSyntax());
            Assert.Equal(expectedLocalKind, symbol.GetSymbol<LocalSymbol>().DeclarationKind);
            Assert.False(((ILocalSymbol)symbol).IsFixed);
            Assert.Same(symbol, model.GetDeclaredSymbol((SyntaxNode)variableDeclaratorSyntax));

            var other = model.LookupSymbols(decl.SpanStart, name: decl.Identifier().ValueText).Single();
            if (isShadowed)
            {
                Assert.NotEqual(symbol, other);
            }
            else
            {
                Assert.Same(symbol, other);
            }

            Assert.True(model.LookupNames(decl.SpanStart).Contains(decl.Identifier().ValueText));

            var local = (ILocalSymbol)symbol;

            AssertInfoForDeclarationExpressionSyntax(model, decl, expectedSymbol: local, expectedType: local.Type);

            foreach (var reference in references)
            {
                Assert.Same(symbol, model.GetSymbolInfo(reference).Symbol);
                Assert.Same(symbol, model.LookupSymbols(reference.SpanStart, name: decl.Identifier().ValueText).Single());
                Assert.True(model.LookupNames(reference.SpanStart).Contains(decl.Identifier().ValueText));
                Assert.Equal(local.Type, model.GetTypeInfo(reference).Type);
            }

            if (verifyDataFlow)
            {
                VerifyDataFlow(model, decl, isDelegateCreation, isExecutableCode, references, symbol);
            }
        }

        private static void AssertInfoForDeclarationExpressionSyntax(
            SemanticModel model,
            DeclarationExpressionSyntax decl,
            ISymbol expectedSymbol = null,
            ITypeSymbol expectedType = null
            )
        {
            var symbolInfo = model.GetSymbolInfo(decl);
            Assert.Equal(expectedSymbol, symbolInfo.Symbol);
            Assert.Empty(symbolInfo.CandidateSymbols);
            Assert.Equal(CandidateReason.None, symbolInfo.CandidateReason);
            Assert.Equal(symbolInfo, ((CSharpSemanticModel)model).GetSymbolInfo(decl));

            var typeInfo = model.GetTypeInfo(decl);
            Assert.Equal(expectedType, typeInfo.Type);

            // skip cases where operation is not supported
            AssertTypeFromOperation(model, expectedType, decl);

            // Note: the following assertion is not, in general, correct for declaration expressions,
            // even though this helper is used to handle declaration expressions.
            // However, the tests that use this helper have been carefully crafted to avoid
            // triggering failure of the assertion. See also https://github.com/dotnet/roslyn/issues/17463
            Assert.Equal(expectedType, typeInfo.ConvertedType);

            Assert.Equal(typeInfo, ((CSharpSemanticModel)model).GetTypeInfo(decl));

            // Note: the following assertion is not, in general, correct for declaration expressions,
            // even though this helper is used to handle declaration expressions.
            // However, the tests that use this helper have been carefully crafted to avoid
            // triggering failure of the assertion. See also https://github.com/dotnet/roslyn/issues/17463
            Assert.True(model.GetConversion(decl).IsIdentity);

            var typeSyntax = decl.Type;

            Assert.True(SyntaxFacts.IsInNamespaceOrTypeContext(typeSyntax));
            Assert.True(SyntaxFacts.IsInTypeOnlyContext(typeSyntax));

            ITypeSymbol expected = expectedSymbol?.GetTypeOrReturnType();

            if (expected?.IsErrorType() != false)
            {
                Assert.Null(model.GetSymbolInfo(typeSyntax).Symbol);
            }
            else
            {
                Assert.Equal(expected, model.GetSymbolInfo(typeSyntax).Symbol);
            }

            typeInfo = model.GetTypeInfo(typeSyntax);
            Assert.Equal(expected, typeInfo.Type);
            Assert.Equal(expected, typeInfo.ConvertedType);
            Assert.Equal(typeInfo, ((CSharpSemanticModel)model).GetTypeInfo(typeSyntax));
            Assert.True(model.GetConversion(typeSyntax).IsIdentity);

            var conversion = model.ClassifyConversion(decl, model.Compilation.ObjectType, false);
            Assert.False(conversion.Exists);
            Assert.Equal(conversion, model.ClassifyConversion(decl, model.Compilation.ObjectType, true));
            Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl, model.Compilation.ObjectType, false));
            Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl, model.Compilation.ObjectType, true));
            Assert.Equal(conversion, model.ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, false));
            Assert.Equal(conversion, model.ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, true));
            Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, false));
            Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, true));

            Assert.Null(model.GetDeclaredSymbol(decl));
        }

        private static void AssertTypeFromOperation(SemanticModel model, ITypeSymbol expectedType, DeclarationExpressionSyntax decl)
        {
            // see https://github.com/dotnet/roslyn/issues/23006 and https://github.com/dotnet/roslyn/issues/23007 for more detail

            // unlike GetSymbolInfo or GetTypeInfo, GetOperation doesn't use SemanticModel's recovery mode.
            // what that means is that GetOperation might return null for ones GetSymbol/GetTypeInfo do return info from
            // error recovery mode
            var typeofExpression = decl.Ancestors().OfType<TypeOfExpressionSyntax>().FirstOrDefault();
            if (typeofExpression?.Type?.FullSpan.Contains(decl.Span) == true)
            {
                // invalid syntax case where operation is not supported
                return;
            }

            Assert.Equal(expectedType, model.GetOperation(decl)?.Type);
        }

        private static void VerifyDataFlow(SemanticModel model, DeclarationExpressionSyntax decl, bool isDelegateCreation, bool isExecutableCode, IdentifierNameSyntax[] references, ISymbol symbol)
        {
            var dataFlowParent = decl.Parent.Parent.Parent as ExpressionSyntax;

            if (dataFlowParent == null)
            {
                if (isExecutableCode || !(decl.Parent.Parent.Parent is VariableDeclaratorSyntax))
                {
                    Assert.IsAssignableFrom<ConstructorInitializerSyntax>(decl.Parent.Parent.Parent);
                }

                return;
            }

            if (model.IsSpeculativeSemanticModel)
            {
                Assert.Throws<NotSupportedException>(() => model.AnalyzeDataFlow(dataFlowParent));
                return;
            }

            var dataFlow = model.AnalyzeDataFlow(dataFlowParent);

            if (isExecutableCode)
            {
                Assert.True(dataFlow.Succeeded);
                Assert.True(dataFlow.VariablesDeclared.Contains(symbol, ReferenceEqualityComparer.Instance));

                if (!isDelegateCreation)
                {
                    Assert.True(dataFlow.AlwaysAssigned.Contains(symbol, ReferenceEqualityComparer.Instance));
                    Assert.True(dataFlow.WrittenInside.Contains(symbol, ReferenceEqualityComparer.Instance));

                    var flowsIn = FlowsIn(dataFlowParent, decl, references);
                    Assert.Equal(flowsIn,
                                 dataFlow.DataFlowsIn.Contains(symbol, ReferenceEqualityComparer.Instance));
                    Assert.Equal(flowsIn,
                                 dataFlow.ReadInside.Contains(symbol, ReferenceEqualityComparer.Instance));

                    Assert.Equal(FlowsOut(dataFlowParent, decl, references),
                                 dataFlow.DataFlowsOut.Contains(symbol, ReferenceEqualityComparer.Instance));
                    Assert.Equal(ReadOutside(dataFlowParent, references),
                                 dataFlow.ReadOutside.Contains(symbol, ReferenceEqualityComparer.Instance));

                    Assert.Equal(WrittenOutside(dataFlowParent, references),
                                 dataFlow.WrittenOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
                }
            }
        }

        private static void VerifyModelForOutVarDuplicateInSameScope(SemanticModel model, DeclarationExpressionSyntax decl)
        {
            var variableDesignationSyntax = GetVariableDesignation(decl);
            var symbol = model.GetDeclaredSymbol(variableDesignationSyntax);
            Assert.Equal(decl.Identifier().ValueText, symbol.Name);
            Assert.Equal(variableDesignationSyntax, symbol.DeclaringSyntaxReferences.Single().GetSyntax());
            Assert.Equal(LocalDeclarationKind.OutVariable, symbol.GetSymbol<LocalSymbol>().DeclarationKind);
            Assert.Same(symbol, model.GetDeclaredSymbol((SyntaxNode)variableDesignationSyntax));
            Assert.NotEqual(symbol, model.LookupSymbols(decl.SpanStart, name: decl.Identifier().ValueText).Single());
            Assert.True(model.LookupNames(decl.SpanStart).Contains(decl.Identifier().ValueText));

            var local = (ILocalSymbol)symbol;

            AssertInfoForDeclarationExpressionSyntax(model, decl, local, local.Type);
        }

        private static void VerifyNotInScope(SemanticModel model, IdentifierNameSyntax reference)
        {
            Assert.Null(model.GetSymbolInfo(reference).Symbol);
            Assert.False(model.LookupSymbols(reference.SpanStart, name: reference.Identifier.ValueText).Any());
            Assert.False(model.LookupNames(reference.SpanStart).Contains(reference.Identifier.ValueText));
        }

        private static void VerifyNotAnOutField(SemanticModel model, IdentifierNameSyntax reference)
        {
            var symbol = model.GetSymbolInfo(reference).Symbol;

            Assert.NotEqual(SymbolKind.Field, symbol.Kind);

            Assert.Same(symbol, model.LookupSymbols(reference.SpanStart, name: reference.Identifier.ValueText).Single());
            Assert.True(model.LookupNames(reference.SpanStart).Contains(reference.Identifier.ValueText));
        }

        internal static void VerifyNotAnOutLocal(SemanticModel model, IdentifierNameSyntax reference)
        {
            var symbol = model.GetSymbolInfo(reference).Symbol;

            if (symbol.Kind == SymbolKind.Local)
            {
                var local = symbol.GetSymbol<SourceLocalSymbol>();
                var parent = local.IdentifierToken.Parent;

                Assert.Empty(parent.Ancestors().OfType<DeclarationExpressionSyntax>().Where(e => e.IsOutVarDeclaration()));

                if (parent.Kind() == SyntaxKind.VariableDeclarator)
                {
                    var parent1 = ((VariableDeclarationSyntax)((VariableDeclaratorSyntax)parent).Parent).Parent;
                    switch (parent1.Kind())
                    {
                        case SyntaxKind.FixedStatement:
                        case SyntaxKind.ForStatement:
                        case SyntaxKind.UsingStatement:
                            break;
                        default:
                            Assert.Equal(SyntaxKind.LocalDeclarationStatement, parent1.Kind());
                            break;
                    }
                }
            }

            Assert.Same(symbol, model.LookupSymbols(reference.SpanStart, name: reference.Identifier.ValueText).Single());
            Assert.True(model.LookupNames(reference.SpanStart).Contains(reference.Identifier.ValueText));
        }

        private static SingleVariableDesignationSyntax GetVariableDesignation(DeclarationExpressionSyntax decl)
        {
            return (SingleVariableDesignationSyntax)decl.Designation;
        }

        private static bool FlowsIn(ExpressionSyntax dataFlowParent, DeclarationExpressionSyntax decl, IdentifierNameSyntax[] references)
        {
            foreach (var reference in references)
            {
                if (dataFlowParent.Span.Contains(reference.Span) && reference.SpanStart > decl.SpanStart)
                {
                    if (IsRead(reference))
                    {
                        return true;
                    }
                }
            }

            return false;
        }

        private static bool IsRead(IdentifierNameSyntax reference)
        {
            switch (reference.Parent.Kind())
            {
                case SyntaxKind.Argument:
                    if (((ArgumentSyntax)reference.Parent).RefOrOutKeyword.Kind() != SyntaxKind.OutKeyword)
                    {
                        return true;
                    }
                    break;

                case SyntaxKind.SimpleAssignmentExpression:
                case SyntaxKind.AddAssignmentExpression:
                case SyntaxKind.AndAssignmentExpression:
                case SyntaxKind.DivideAssignmentExpression:
                case SyntaxKind.ExclusiveOrAssignmentExpression:
                case SyntaxKind.LeftShiftAssignmentExpression:
                case SyntaxKind.ModuloAssignmentExpression:
                case SyntaxKind.MultiplyAssignmentExpression:
                case SyntaxKind.OrAssignmentExpression:
                case SyntaxKind.RightShiftAssignmentExpression:
                case SyntaxKind.SubtractAssignmentExpression:
                    if (((AssignmentExpressionSyntax)reference.Parent).Left != reference)
                    {
                        return true;
                    }
                    break;

                default:
                    return true;
            }

            return false;
        }

        private static bool ReadOutside(ExpressionSyntax dataFlowParent, IdentifierNameSyntax[] references)
        {
            foreach (var reference in references)
            {
                if (!dataFlowParent.Span.Contains(reference.Span))
                {
                    if (IsRead(reference))
                    {
                        return true;
                    }
                }
            }

            return false;
        }

        private static bool FlowsOut(ExpressionSyntax dataFlowParent, DeclarationExpressionSyntax decl, IdentifierNameSyntax[] references)
        {
            ForStatementSyntax forStatement;

            if ((forStatement = decl.Ancestors().OfType<ForStatementSyntax>().FirstOrDefault()) != null &&
                 forStatement.Incrementors.Span.Contains(decl.Position) &&
                 forStatement.Statement.DescendantNodes().OfType<ForStatementSyntax>().Any(f => f.Condition == null))
            {
                return false;
            }

            var containingStatement = decl.Ancestors().OfType<StatementSyntax>().FirstOrDefault();
            var containingReturnOrThrow = containingStatement as ReturnStatementSyntax ?? (StatementSyntax)(containingStatement as ThrowStatementSyntax);

            MethodDeclarationSyntax methodDeclParent;

            if (containingReturnOrThrow != null && decl.Identifier().ValueText == "x1" &&
                ((methodDeclParent = containingReturnOrThrow.Parent.Parent as MethodDeclarationSyntax) == null ||
                  methodDeclParent.Body.Statements.First() != containingReturnOrThrow))
            {
                return false;
            }

            foreach (var reference in references)
            {
                if (!dataFlowParent.Span.Contains(reference.Span) &&
                    (containingReturnOrThrow == null || containingReturnOrThrow.Span.Contains(reference.SpanStart)) &&
                    (reference.SpanStart > decl.SpanStart ||
                     (containingReturnOrThrow == null &&
                     reference.Ancestors().OfType<DoStatementSyntax>().Join(
                         decl.Ancestors().OfType<DoStatementSyntax>(), d => d, d => d, (d1, d2) => true).Any())))
                {
                    if (IsRead(reference))
                    {
                        return true;
                    }
                }
            }

            return false;
        }

        private static bool WrittenOutside(ExpressionSyntax dataFlowParent, IdentifierNameSyntax[] references)
        {
            foreach (var reference in references)
            {
                if (!dataFlowParent.Span.Contains(reference.Span))
                {
                    if (IsWrite(reference))
                    {
                        return true;
                    }
                }
            }

            return false;
        }

        private static bool IsWrite(IdentifierNameSyntax reference)
        {
            switch (reference.Parent.Kind())
            {
                case SyntaxKind.Argument:
                    if (((ArgumentSyntax)reference.Parent).RefOrOutKeyword.Kind() != SyntaxKind.None)
                    {
                        return true;
                    }
                    break;

                case SyntaxKind.SimpleAssignmentExpression:
                case SyntaxKind.AddAssignmentExpression:
                case SyntaxKind.AndAssignmentExpression:
                case SyntaxKind.DivideAssignmentExpression:
                case SyntaxKind.ExclusiveOrAssignmentExpression:
                case SyntaxKind.LeftShiftAssignmentExpression:
                case SyntaxKind.ModuloAssignmentExpression:
                case SyntaxKind.MultiplyAssignmentExpression:
                case SyntaxKind.OrAssignmentExpression:
                case SyntaxKind.RightShiftAssignmentExpression:
                case SyntaxKind.SubtractAssignmentExpression:
                    if (((AssignmentExpressionSyntax)reference.Parent).Left == reference)
                    {
                        return true;
                    }
                    break;

                case SyntaxKind.PreIncrementExpression:
                case SyntaxKind.PostIncrementExpression:
                case SyntaxKind.PreDecrementExpression:
                case SyntaxKind.PostDecrementExpression:
                    return true;

                default:
                    return false;
            }

            return false;
        }

        [Fact]
        public void Simple_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out System.Int32 x1), x1);
        int x2 = 0;
        Test3(x2);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, int y)
    {
        System.Console.WriteLine(y);
    }

    static void Test3(int y)
    {
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Ref = GetReference(tree, "x2");
            Assert.Null(model.GetDeclaredSymbol(x2Ref));
            Assert.Null(model.GetDeclaredSymbol((ArgumentSyntax)x2Ref.Parent));
        }

        [Fact]
        public void Simple_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out (int, int) x1), x1);
    }

    static object Test1(out (int, int) x)
    {
        x = (123, 124);
        return null;
    }

    static void Test2(object x, (int, int) y)
    {
        System.Console.WriteLine(y);
    }
}

namespace System
{
    // struct with two values
    public struct ValueTuple<T1, T2>
    {
        public T1 Item1;
        public T2 Item2;
        public ValueTuple(T1 item1, T2 item2)
        {
            this.Item1 = item1;
            this.Item2 = item2;
        }
        public override string ToString()
        {
            return '{' + Item1?.ToString() + "", "" + Item2?.ToString() + '}';
        }
    }
}
" + TestResources.NetFX.ValueTuple.tupleattributes_cs;
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"{123, 124}").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Simple_04()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out System.Collections.Generic.IEnumerable<System.Int32> x1), x1);
    }

    static object Test1(out System.Collections.Generic.IEnumerable<System.Int32> x)
    {
        x = new System.Collections.Generic.List<System.Int32>();
        return null;
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"System.Collections.Generic.List`1[System.Int32]").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Simple_05()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int x1, out x1), x1);
    }

    static object Test1(out int x, out int y)
    {
        x = 123;
        y = 124;
        return null;
    }

    static void Test2(object x, int y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"124").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1", 2);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Simple_06()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int x1, x1 = 124), x1);
    }

    static object Test1(out int x, int y)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, int y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1", 2);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Simple_07()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int x1), x1, x1 = 124);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, int y, int z)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1", 2);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Simple_08()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int x1), ref x1);
        int x2 = 0;
        Test3(ref x2);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, ref int y)
    {
        System.Console.WriteLine(y);
    }

    static void Test3(ref int y)
    {
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Ref = GetReference(tree, "x2");
            Assert.Null(model.GetDeclaredSymbol(x2Ref));
            Assert.Null(model.GetDeclaredSymbol((ArgumentSyntax)x2Ref.Parent));
        }

        [Fact]
        public void Simple_09()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int x1), out x1);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, out int y)
    {
        y = 0;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Simple_10()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out dynamic x1), x1);
    }

    static object Test1(out dynamic x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            references: new MetadataReference[] { CSharpRef },
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Simple_11()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out int[] x1), x1);
    }

    static object Test1(out int[] x)
    {
        x = new [] {123};
        return null;
    }

    static void Test2(object x, int[] y)
    {
        System.Console.WriteLine(y[0]);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Scope_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        int x1 = 0;
        Test1(out int x1);
        Test2(Test1(out int x2), 
                    out int x2);
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }

    static void Test2(object y, out int x)
    {
        x = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,23): error CS0128: A local variable named 'x1' is already defined in this scope
                //         Test1(out int x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(7, 23),
                // (9,29): error CS0128: A local variable named 'x2' is already defined in this scope
                //                     out int x2);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(9, 29),
                // (6,13): warning CS0219: The variable 'x1' is assigned but its value is never used
                //         int x1 = 0;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x1").WithArguments("x1").WithLocation(6, 13)
                );
        }

        [Fact]
        public void Scope_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(x1, 
              Test1(out int x1));
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }

    static void Test2(object y, object x)
    {
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,15): error CS0841: Cannot use local variable 'x1' before it is declared
                //         Test2(x1, 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(6, 15)
                );
        }

        [Fact]
        public void Scope_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(out x1, 
              Test1(out int x1));
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }

    static void Test2(out int y, object x)
    {
        y = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,19): error CS0841: Cannot use local variable 'x1' before it is declared
                //         Test2(out x1, 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(6, 19)
                );
        }

        [Fact]
        public void Scope_04()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out int x1);
        System.Console.WriteLine(x1);
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: "1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Scope_05()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(out x1, 
              Test1(out var x1));
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }

    static void Test2(out int y, object x)
    {
        y = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,19): error CS0841: Cannot use local variable 'x1' before it is declared
                //         Test2(out x1, 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(6, 19)
                );
        }

        [Fact]
        public void Scope_Attribute_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    [Test(p = TakeOutParam(out int x3) && x3 > 0)]
    [Test(p = x4 && TakeOutParam(out int x4))]
    [Test(p = TakeOutParam(51, out int x5) && 
              TakeOutParam(52, out int x5) && 
              x5 > 0)]
    [Test(p1 = TakeOutParam(out int x6) && x6 > 0, 
          p2 = TakeOutParam(out int x6) && x6 > 0)]
    [Test(p = TakeOutParam(out int x7) && x7 > 0)]
    [Test(p = x7 > 2)]
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public bool p {get; set;}
    public bool p1 {get; set;}
    public bool p2 {get; set;}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p = TakeOutParam(out int x3) && x3 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x3) && x3 > 0").WithLocation(8, 15),
                // (9,15): error CS0841: Cannot use local variable 'x4' before it is declared
                //     [Test(p = x4 && TakeOutParam(out int x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(9, 15),
                // (11,40): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //               TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(11, 40),
                // (10,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p = TakeOutParam(51, out int x5) && 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, @"TakeOutParam(51, out int x5) && 
              TakeOutParam(52, out int x5) && 
              x5 > 0").WithLocation(10, 15),
                // (14,37): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //           p2 = TakeOutParam(out int x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(14, 37),
                // (13,16): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p1 = TakeOutParam(out int x6) && x6 > 0, 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x6) && x6 > 0").WithLocation(13, 16),
                // (14,16): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //           p2 = TakeOutParam(out int x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x6) && x6 > 0").WithLocation(14, 16),
                // (15,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p = TakeOutParam(out int x7) && x7 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x7) && x7 > 0").WithLocation(15, 15),
                // (16,15): error CS0103: The name 'x7' does not exist in the current context
                //     [Test(p = x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(16, 15),
                // (17,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(17, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_Attribute_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    [Test(TakeOutParam(out int x3) && x3 > 0)]
    [Test(x4 && TakeOutParam(out int x4))]
    [Test(TakeOutParam(51, out int x5) && 
          TakeOutParam(52, out int x5) && 
          x5 > 0)]
    [Test(TakeOutParam(out int x6) && x6 > 0, 
          TakeOutParam(out int x6) && x6 > 0)]
    [Test(TakeOutParam(out int x7) && x7 > 0)]
    [Test(x7 > 2)]
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public Test(bool p) {}
    public Test(bool p1, bool p2) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(out int x3) && x3 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x3) && x3 > 0").WithLocation(8, 11),
                // (9,11): error CS0841: Cannot use local variable 'x4' before it is declared
                //     [Test(x4 && TakeOutParam(out int x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(9, 11),
                // (11,36): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //           TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(11, 36),
                // (10,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(51, out int x5) && 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, @"TakeOutParam(51, out int x5) && 
          TakeOutParam(52, out int x5) && 
          x5 > 0").WithLocation(10, 11),
                // (14,32): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //           TakeOutParam(out int x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(14, 32),
                // (13,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(out int x6) && x6 > 0, 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x6) && x6 > 0").WithLocation(13, 11),
                // (14,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //           TakeOutParam(out int x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x6) && x6 > 0").WithLocation(14, 11),
                // (15,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(out int x7) && x7 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out int x7) && x7 > 0").WithLocation(15, 11),
                // (16,11): error CS0103: The name 'x7' does not exist in the current context
                //     [Test(x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(16, 11),
                // (17,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(17, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_Attribute_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    [Test(p = TakeOutParam(out var x3) && x3 > 0)]
    [Test(p = x4 && TakeOutParam(out var x4))]
    [Test(p = TakeOutParam(51, out var x5) && 
              TakeOutParam(52, out var x5) && 
              x5 > 0)]
    [Test(p1 = TakeOutParam(out var x6) && x6 > 0, 
          p2 = TakeOutParam(out var x6) && x6 > 0)]
    [Test(p = TakeOutParam(out var x7) && x7 > 0)]
    [Test(p = x7 > 2)]
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public bool p {get; set;}
    public bool p1 {get; set;}
    public bool p2 {get; set;}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p = TakeOutParam(out var x3) && x3 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x3) && x3 > 0").WithLocation(8, 15),
                // (9,15): error CS0841: Cannot use local variable 'x4' before it is declared
                //     [Test(p = x4 && TakeOutParam(out var x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(9, 15),
                // (11,40): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //               TakeOutParam(52, out var x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(11, 40),
                // (10,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p = TakeOutParam(51, out var x5) && 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, @"TakeOutParam(51, out var x5) && 
              TakeOutParam(52, out var x5) && 
              x5 > 0").WithLocation(10, 15),
                // (14,37): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //           p2 = TakeOutParam(out var x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(14, 37),
                // (13,16): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p1 = TakeOutParam(out var x6) && x6 > 0, 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x6) && x6 > 0").WithLocation(13, 16),
                // (14,16): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //           p2 = TakeOutParam(out var x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x6) && x6 > 0").WithLocation(14, 16),
                // (15,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(p = TakeOutParam(out var x7) && x7 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x7) && x7 > 0").WithLocation(15, 15),
                // (16,15): error CS0103: The name 'x7' does not exist in the current context
                //     [Test(p = x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(16, 15),
                // (17,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(17, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_Attribute_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    [Test(TakeOutParam(out var x3) && x3 > 0)]
    [Test(x4 && TakeOutParam(out var x4))]
    [Test(TakeOutParam(51, out var x5) && 
          TakeOutParam(52, out var x5) && 
          x5 > 0)]
    [Test(TakeOutParam(out var x6) && x6 > 0, 
          TakeOutParam(out var x6) && x6 > 0)]
    [Test(TakeOutParam(out var x7) && x7 > 0)]
    [Test(x7 > 2)]
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public Test(bool p) {}
    public Test(bool p1, bool p2) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(out var x3) && x3 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x3) && x3 > 0").WithLocation(8, 11),
                // (9,11): error CS0841: Cannot use local variable 'x4' before it is declared
                //     [Test(x4 && TakeOutParam(out var x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(9, 11),
                // (11,36): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //           TakeOutParam(52, out var x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(11, 36),
                // (10,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(51, out var x5) && 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, @"TakeOutParam(51, out var x5) && 
          TakeOutParam(52, out var x5) && 
          x5 > 0").WithLocation(10, 11),
                // (14,32): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //           TakeOutParam(out var x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(14, 32),
                // (13,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(out var x6) && x6 > 0, 
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x6) && x6 > 0").WithLocation(13, 11),
                // (14,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //           TakeOutParam(out var x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x6) && x6 > 0").WithLocation(14, 11),
                // (15,11): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //     [Test(TakeOutParam(out var x7) && x7 > 0)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "TakeOutParam(out var x7) && x7 > 0").WithLocation(15, 11),
                // (16,11): error CS0103: The name 'x7' does not exist in the current context
                //     [Test(x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(16, 11),
                // (17,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(17, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void AttributeArgument_01()
        {
            var source =
@"
public class X
{
    [Test(out var x3)]
    [Test(out int x4)]
    [Test(p: out var x5)]
    [Test(p: out int x6)]
    public static void Main()
    {
    }
}

class Test : System.Attribute
{
    public Test(out int p) { p = 100; }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_1);
            compilation.VerifyDiagnostics(
                // (4,11): error CS1041: Identifier expected; 'out' is a keyword
                //     [Test(out var x3)]
                Diagnostic(ErrorCode.ERR_IdentifierExpectedKW, "out").WithArguments("", "out").WithLocation(4, 11),
                // (4,19): error CS1003: Syntax error, ',' expected
                //     [Test(out var x3)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "x3").WithArguments(",").WithLocation(4, 19),
                // (5,11): error CS1041: Identifier expected; 'out' is a keyword
                //     [Test(out int x4)]
                Diagnostic(ErrorCode.ERR_IdentifierExpectedKW, "out").WithArguments("", "out").WithLocation(5, 11),
                // (5,15): error CS1525: Invalid expression term 'int'
                //     [Test(out int x4)]
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, "int").WithArguments("int").WithLocation(5, 15),
                // (5,19): error CS1003: Syntax error, ',' expected
                //     [Test(out int x4)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "x4").WithArguments(",").WithLocation(5, 19),
                // (6,14): error CS1525: Invalid expression term 'out'
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, "out").WithArguments("out").WithLocation(6, 14),
                // (6,14): error CS1003: Syntax error, ',' expected
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "out").WithArguments(",").WithLocation(6, 14),
                // (6,18): error CS1003: Syntax error, ',' expected
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "var").WithArguments(",").WithLocation(6, 18),
                // (6,22): error CS1003: Syntax error, ',' expected
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "x5").WithArguments(",").WithLocation(6, 22),
                // (7,14): error CS1525: Invalid expression term 'out'
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, "out").WithArguments("out").WithLocation(7, 14),
                // (7,14): error CS1003: Syntax error, ',' expected
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "out").WithArguments(",").WithLocation(7, 14),
                // (7,18): error CS1003: Syntax error, ',' expected
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "int").WithArguments(",").WithLocation(7, 18),
                // (7,18): error CS1525: Invalid expression term 'int'
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, "int").WithArguments("int").WithLocation(7, 18),
                // (7,22): error CS1003: Syntax error, ',' expected
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_SyntaxError, "x6").WithArguments(",").WithLocation(7, 22),
                // (4,15): error CS0103: The name 'var' does not exist in the current context
                //     [Test(out var x3)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(4, 15),
                // (4,19): error CS0103: The name 'x3' does not exist in the current context
                //     [Test(out var x3)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x3").WithArguments("x3").WithLocation(4, 19),
                // (4,6): error CS1729: 'Test' does not contain a constructor that takes 2 arguments
                //     [Test(out var x3)]
                Diagnostic(ErrorCode.ERR_BadCtorArgCount, "Test(out var x3)").WithArguments("Test", "2").WithLocation(4, 6),
                // (5,19): error CS0103: The name 'x4' does not exist in the current context
                //     [Test(out int x4)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(5, 19),
                // (5,6): error CS1729: 'Test' does not contain a constructor that takes 2 arguments
                //     [Test(out int x4)]
                Diagnostic(ErrorCode.ERR_BadCtorArgCount, "Test(out int x4)").WithArguments("Test", "2").WithLocation(5, 6),
                // (6,18): error CS0103: The name 'var' does not exist in the current context
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(6, 18),
                // (6,18): error CS1738: Named argument specifications must appear after all fixed arguments have been specified. Please use language version 7.2 or greater to allow non-trailing named arguments.
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_NamedArgumentSpecificationBeforeFixedArgument, "var").WithArguments("7.2").WithLocation(6, 18),
                // (6,22): error CS0103: The name 'x5' does not exist in the current context
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(6, 22),
                // (6,6): error CS1729: 'Test' does not contain a constructor that takes 3 arguments
                //     [Test(p: out var x5)]
                Diagnostic(ErrorCode.ERR_BadCtorArgCount, "Test(p: out var x5)").WithArguments("Test", "3").WithLocation(6, 6),
                // (7,18): error CS1738: Named argument specifications must appear after all fixed arguments have been specified. Please use language version 7.2 or greater to allow non-trailing named arguments.
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_NamedArgumentSpecificationBeforeFixedArgument, "int").WithArguments("7.2").WithLocation(7, 18),
                // (7,22): error CS0103: The name 'x6' does not exist in the current context
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x6").WithArguments("x6").WithLocation(7, 22),
                // (7,6): error CS1729: 'Test' does not contain a constructor that takes 3 arguments
                //     [Test(p: out int x6)]
                Diagnostic(ErrorCode.ERR_BadCtorArgCount, "Test(p: out int x6)").WithArguments("Test", "3").WithLocation(7, 6)
                );

            var tree = compilation.SyntaxTrees.Single();

            Assert.False(GetOutVarDeclarations(tree, "x3").Any());
            Assert.False(GetOutVarDeclarations(tree, "x4").Any());
            Assert.False(GetOutVarDeclarations(tree, "x5").Any());
            Assert.False(GetOutVarDeclarations(tree, "x6").Any());
        }

        [Fact]
        public void Scope_Catch_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        try {}
        catch when (TakeOutParam(out var x1) && x1 > 0)
        {
            Dummy(x1);
        }
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        try {}
        catch when (TakeOutParam(out var x4) && x4 > 0)
        {
            Dummy(x4);
        }
    }

    void Test6()
    {
        try {}
        catch when (x6 && TakeOutParam(out var x6))
        {
            Dummy(x6);
        }
    }

    void Test7()
    {
        try {}
        catch when (TakeOutParam(out var x7) && x7 > 0)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        try {}
        catch when (TakeOutParam(out var x8) && x8 > 0)
        {
            Dummy(x8);
        }

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        try {}
        catch when (TakeOutParam(out var x9) && x9 > 0)
        {   
            Dummy(x9);
            try {}
            catch when (TakeOutParam(out var x9) && x9 > 0) // 2
            {
                Dummy(x9);
            }
        }
    }

    void Test10()
    {
        try {}
        catch when (TakeOutParam(y10, out var x10))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    try {}
    //    catch when (TakeOutParam(y11, out var x11)
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test14()
    {
        try {}
        catch when (Dummy(TakeOutParam(out var x14), 
                          TakeOutParam(out var x14), // 2
                          x14))
        {
            Dummy(x14);
        }
    }

    void Test15()
    {
        try {}
        catch (System.Exception x15)
              when (Dummy(TakeOutParam(out var x15), x15))
        {
            Dummy(x15);
        }
    }

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (25,42): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         catch when (TakeOutParam(out var x4) && x4 > 0)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(25, 42),
                // (34,21): error CS0841: Cannot use local variable 'x6' before it is declared
                //         catch when (x6 && TakeOutParam(out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(34, 21),
                // (45,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(45, 17),
                // (58,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(58, 34),
                // (68,46): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             catch when (TakeOutParam(out var x9) && x9 > 0) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(68, 46),
                // (78,34): error CS0103: The name 'y10' does not exist in the current context
                //         catch when (TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(78, 34),
                // (99,48): error CS0128: A local variable named 'x14' is already defined in this scope
                //                           TakeOutParam(out var x14), // 2
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 48),
                // (110,48): error CS0128: A local variable named 'x15' is already defined in this scope
                //               when (Dummy(TakeOutParam(out var x15), x15))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x15").WithArguments("x15").WithLocation(110, 48)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclaration(tree, "x6");
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclaration(tree, "x8");
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

            var x15Decl = GetOutVarDeclaration(tree, "x15");
            var x15Ref = GetReferences(tree, "x15").ToArray();
            Assert.Equal(2, x15Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x15Decl);
            VerifyNotAnOutLocal(model, x15Ref[0]);
            VerifyNotAnOutLocal(model, x15Ref[1]);
        }

        [Fact]
        public void Scope_Catch_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        try {}
        catch when (TakeOutParam(out int x1) && x1 > 0)
        {
            Dummy(x1);
        }
    }

    void Test4()
    {
        int x4 = 11;
        Dummy(x4);

        try {}
        catch when (TakeOutParam(out int x4) && x4 > 0)
        {
            Dummy(x4);
        }
    }

    void Test6()
    {
        try {}
        catch when (x6 && TakeOutParam(out int x6))
        {
            Dummy(x6);
        }
    }

    void Test7()
    {
        try {}
        catch when (TakeOutParam(out int x7) && x7 > 0)
        {
            int x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        try {}
        catch when (TakeOutParam(out int x8) && x8 > 0)
        {
            Dummy(x8);
        }

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        try {}
        catch when (TakeOutParam(out int x9) && x9 > 0)
        {   
            Dummy(x9);
            try {}
            catch when (TakeOutParam(out int x9) && x9 > 0) // 2
            {
                Dummy(x9);
            }
        }
    }

    void Test10()
    {
        try {}
        catch when (TakeOutParam(y10, out int x10))
        {   
            int y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    try {}
    //    catch when (TakeOutParam(y11, out int x11)
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test14()
    {
        try {}
        catch when (Dummy(TakeOutParam(out int x14), 
                          TakeOutParam(out int x14), // 2
                          x14))
        {
            Dummy(x14);
        }
    }

    void Test15()
    {
        try {}
        catch (System.Exception x15)
              when (Dummy(TakeOutParam(out int x15), x15))
        {
            Dummy(x15);
        }
    }

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (25,42): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         catch when (TakeOutParam(out int x4) && x4 > 0)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(25, 42),
                // (34,21): error CS0841: Cannot use local variable 'x6' before it is declared
                //         catch when (x6 && TakeOutParam(out int x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(34, 21),
                // (45,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             int x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(45, 17),
                // (58,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(58, 34),
                // (68,46): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             catch when (TakeOutParam(out int x9) && x9 > 0) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(68, 46),
                // (78,34): error CS0103: The name 'y10' does not exist in the current context
                //         catch when (TakeOutParam(y10, out int x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(78, 34),
                // (99,48): error CS0128: A local variable named 'x14' is already defined in this scope
                //                           TakeOutParam(out int x14), // 2
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 48),
                // (110,48): error CS0128: A local variable named 'x15' is already defined in this scope
                //               when (Dummy(TakeOutParam(out int x15), x15))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x15").WithArguments("x15").WithLocation(110, 48)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclaration(tree, "x6");
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclaration(tree, "x8");
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

            var x15Decl = GetOutVarDeclaration(tree, "x15");
            var x15Ref = GetReferences(tree, "x15").ToArray();
            Assert.Equal(2, x15Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x15Decl);
            VerifyNotAnOutLocal(model, x15Ref[0]);
            VerifyNotAnOutLocal(model, x15Ref[1]);
        }

        [Fact]
        public void Catch_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        try
        {
            throw new System.InvalidOperationException();
        }
        catch (System.Exception e) when (Dummy(TakeOutParam(e, out var x1), x1))
        {
            System.Console.WriteLine(x1.GetType());
        }
    }

    static bool Dummy(object y, object z) 
    {
        System.Console.WriteLine(z.GetType());
        return true;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"System.InvalidOperationException
System.InvalidOperationException");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Catch_01_ExplicitType()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        try
        {
            throw new System.InvalidOperationException();
        }
        catch (System.Exception e) when (Dummy(TakeOutParam(e, out System.Exception x1), x1))
        {
            System.Console.WriteLine(x1.GetType());
        }
    }

    static bool Dummy(object y, object z) 
    {
        System.Console.WriteLine(z.GetType());
        return true;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"System.InvalidOperationException
System.InvalidOperationException");
        }

        [Fact]
        public void Catch_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        try
        {
            throw new System.InvalidOperationException();
        }
        catch (System.Exception e) when (Dummy(TakeOutParam(e, out var x1), x1))
        {
            System.Action d = () =>
                                {
                                    System.Console.WriteLine(x1.GetType());
                                };

            System.Console.WriteLine(x1.GetType());
            d();
        }
    }

    static bool Dummy(object y, object z) 
    {
        System.Console.WriteLine(z.GetType());
        return true;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"System.InvalidOperationException
System.InvalidOperationException
System.InvalidOperationException");
        }

        [Fact]
        public void Catch_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        try
        {
            throw new System.InvalidOperationException();
        }
        catch (System.Exception e) when (Dummy(TakeOutParam(e, out var x1), x1))
        {
            System.Action d = () =>
                                {
                                    e = new System.NullReferenceException();
                                    System.Console.WriteLine(x1.GetType());
                                };

            System.Console.WriteLine(x1.GetType());
            d();
            System.Console.WriteLine(e.GetType());
        }
    }

    static bool Dummy(object y, object z) 
    {
        System.Console.WriteLine(z.GetType());
        return true;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"System.InvalidOperationException
System.InvalidOperationException
System.InvalidOperationException
System.NullReferenceException");
        }

        [Fact]
        public void Catch_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        try
        {
            throw new System.InvalidOperationException();
        }
        catch (System.Exception e) when (Dummy(TakeOutParam(e, out var x1), x1))
        {
            System.Action d = () =>
                                {
                                    e = new System.NullReferenceException();
                                };

            System.Console.WriteLine(x1.GetType());
            d();
            System.Console.WriteLine(e.GetType());
        }
    }

    static bool Dummy(object y, object z) 
    {
        System.Console.WriteLine(z.GetType());
        return true;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"System.InvalidOperationException
System.InvalidOperationException
System.NullReferenceException");
        }

        [Fact]
        public void Scope_ConstructorInitializers_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    X(byte x)
        : this(TakeOutParam(3, out int x3) && x3 > 0)
    {}

    X(sbyte x)
        : this(x4 && TakeOutParam(4, out int x4))
    {}

    X(short x)
        : this(TakeOutParam(51, out int x5) && 
               TakeOutParam(52, out int x5) && 
               x5 > 0)
    {}

    X(ushort x)
        : this(TakeOutParam(6, out int x6) && x6 > 0, 
               TakeOutParam(6, out int x6) && x6 > 0) // 2
    {}
    X(int x)
        : this(TakeOutParam(7, out int x7) && x7 > 0)
    {}
    X(uint x)
        : this(x7, 2)
    {}
    void Test73() { Dummy(x7, 3); } 

    X(params object[] x) {}
    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,16): error CS0841: Cannot use local variable 'x4' before it is declared
                //         : this(x4 && TakeOutParam(4, out int x4))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(13, 16),
                // (18,41): error CS0128: A local variable named 'x5' is already defined in this scope
                //                TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(18, 41),
                // (24,40): error CS0128: A local variable named 'x6' is already defined in this scope
                //                TakeOutParam(6, out int x6) && x6 > 0) // 2
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(24, 40),
                // (30,16): error CS0103: The name 'x7' does not exist in the current context
                //         : this(x7, 2)
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(30, 16),
                // (32,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(32, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_ConstructorInitializers_02()
        {
            var source =
@"
public class X : Y
{
    public static void Main()
    {
    }

    X(byte x)
        : base(TakeOutParam(3, out int x3) && x3 > 0)
    {}

    X(sbyte x)
        : base(x4 && TakeOutParam(4, out int x4))
    {}

    X(short x)
        : base(TakeOutParam(51, out int x5) && 
               TakeOutParam(52, out int x5) && 
               x5 > 0)
    {}

    X(ushort x)
        : base(TakeOutParam(6, out int x6) && x6 > 0, 
               TakeOutParam(6, out int x6) && x6 > 0) // 2
    {}
    X(int x)
        : base(TakeOutParam(7, out int x7) && x7 > 0)
    {}
    X(uint x)
        : base(x7, 2)
    {}
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}

public class Y
{
    public Y(params object[] x) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,16): error CS0841: Cannot use local variable 'x4' before it is declared
                //         : base(x4 && TakeOutParam(4, out int x4))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(13, 16),
                // (18,41): error CS0128: A local variable named 'x5' is already defined in this scope
                //                TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(18, 41),
                // (24,40): error CS0128: A local variable named 'x6' is already defined in this scope
                //                TakeOutParam(6, out int x6) && x6 > 0) // 2
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(24, 40),
                // (30,16): error CS0103: The name 'x7' does not exist in the current context
                //         : base(x7, 2)
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(30, 16),
                // (32,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(32, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_ConstructorInitializers_03()
        {
            var source =
@"using System;
public class X
{
    public static void Main()
    {
        new D(1);
        new D(10);
        new D(12);
    }
}
class D
{
    public D(int o) : this(TakeOutParam(o, out int x1) && x1 >= 5) 
    {
        Console.WriteLine(x1);
    }

    public D(bool b) { Console.WriteLine(b); }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"False
1
True
10
True
12
").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Scope_ConstructorInitializers_04()
        {
            var source =
@"using System;
public class X
{
    public static void Main()
    {
        new D(1);
        new D(10);
        new D(12);
    }
}
class D : C
{
    public D(int o) : base(TakeOutParam(o, out int x1) && x1 >= 5) 
    {
        Console.WriteLine(x1);
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}

class C
{
    public C(bool b) { Console.WriteLine(b); }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"False
1
True
10
True
12
").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Scope_ConstructorInitializers_05()
        {
            var source =
@"using System;
class D
{
    public D(int o) : this(SpeculateHere) 
    {
    }

    public D(bool b) { Console.WriteLine(b); }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            ArgumentListSyntax arguments = SyntaxFactory.ParseArgumentList(@"(TakeOutParam(o, out int x1) && x1 >= 5)");
            var initializer = SyntaxFactory.ConstructorInitializer(SyntaxKind.ThisConstructorInitializer, arguments);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, initializer, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = initializer.SyntaxTree;

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Scope_ConstructorInitializers_06()
        {
            var source =
@"using System;
class D : C
{
    public D(int o) : base(SpeculateHere) 
    {
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}

class C
{
    public C(bool b) { Console.WriteLine(b); }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            ArgumentListSyntax arguments = SyntaxFactory.ParseArgumentList(@"(TakeOutParam(o, out int x1) && x1 >= 5)");
            var initializer = SyntaxFactory.ConstructorInitializer(SyntaxKind.BaseConstructorInitializer, arguments);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, initializer, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = initializer.SyntaxTree;

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var initializerOperation = model.GetOperation(initializer);

            Assert.Null(initializerOperation.Parent.Parent.Parent);
            VerifyOperationTree(compilation, initializerOperation.Parent.Parent, @"
IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsImplicit) (Syntax: ':base(TakeO ... && x1 >= 5)')
  Expression: 
    IOperation:  (OperationKind.None, Type: System.Void, IsImplicit) (Syntax: '(TakeOutPar ... && x1 >= 5)')
      Children(1):
          IInvocationOperation ( C..ctor(System.Boolean b)) (OperationKind.Invocation, Type: System.Void) (Syntax: ':base(TakeO ... && x1 >= 5)')
            Instance Receiver: 
              IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsImplicit) (Syntax: ':base(TakeO ... && x1 >= 5)')
            Arguments(1):
                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: b) (OperationKind.Argument, Type: null) (Syntax: 'TakeOutPara ...  && x1 >= 5')
                  IBinaryOperation (BinaryOperatorKind.ConditionalAnd) (OperationKind.Binary, Type: System.Boolean) (Syntax: 'TakeOutPara ...  && x1 >= 5')
                    Left: 
                      IInvocationOperation (System.Boolean D.TakeOutParam(System.Int32 y, out System.Int32 x)) (OperationKind.Invocation, Type: System.Boolean) (Syntax: 'TakeOutPara ... out int x1)')
                        Instance Receiver: 
                          null
                        Arguments(2):
                            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: y) (OperationKind.Argument, Type: null) (Syntax: 'o')
                              IParameterReferenceOperation: o (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'o')
                              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null) (Syntax: 'out int x1')
                              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32) (Syntax: 'int x1')
                                ILocalReferenceOperation: x1 (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x1')
                              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                    Right: 
                      IBinaryOperation (BinaryOperatorKind.GreaterThanOrEqual) (OperationKind.Binary, Type: System.Boolean) (Syntax: 'x1 >= 5')
                        Left: 
                          ILocalReferenceOperation: x1 (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x1')
                        Right: 
                          ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 5) (Syntax: '5')
                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
        }

        [Fact]
        public void Scope_ConstructorInitializers_07()
        {
            var source =
@"
public class X : Y
{
    public static void Main()
    {
    }

    X(byte x3)
        : base(TakeOutParam(3, out var x3))
    {}

    X(sbyte x)
        : base(TakeOutParam(4, out var x4))
    {
        int x4 = 1;
        System.Console.WriteLine(x4);
    }

    X(ushort x)
        : base(TakeOutParam(51, out var x5))
    => Dummy(TakeOutParam(52, out var x5), x5);

    X(short x)
        : base(out int x6, x6)
    {}

    X(uint x)
        : base(out var x7, x7)
    {}

    X(int x)
        : base(TakeOutParam(out int x8, x8))
    {}

    X(ulong x)
        : base(TakeOutParam(out var x9, x9))
    {}

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(out int x, int y) 
    {
        x = 123;
        return true;
    }
}

public class Y
{
    public Y(params object[] x) {}
    public Y(out int x, int y) { x = y; }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (9,40): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         : base(TakeOutParam(3, out var x3))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(9, 40),
                // (15,13): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         int x4 = 1;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(15, 13),
                // (21,39): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     => Dummy(TakeOutParam(52, out var x5), x5);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(21, 39),
                // (24,28): error CS0165: Use of unassigned local variable 'x6'
                //         : base(out int x6, x6)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x6").WithArguments("x6").WithLocation(24, 28),
                // (28,28): error CS8196: Reference to an implicitly-typed out variable 'x7' is not permitted in this location.
                //         : base(out var x7, x7)
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableUsedInForbiddenZone, "x7").WithArguments("x7").WithLocation(28, 28),
                // (28,20): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //         : base(out var x7, x7)
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x7").WithArguments("1", "out").WithLocation(28, 20),
                // (32,41): error CS0165: Use of unassigned local variable 'x8'
                //         : base(TakeOutParam(out int x8, x8))
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x8").WithArguments("x8").WithLocation(32, 41),
                // (36,41): error CS8196: Reference to an implicitly-typed out variable 'x9' is not permitted in this location.
                //         : base(TakeOutParam(out var x9, x9))
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableUsedInForbiddenZone, "x9").WithArguments("x9").WithLocation(36, 41)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl);
            VerifyNotAnOutLocal(model, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0]);
            VerifyModelForOutVar(model, x5Decl[1], x5Ref);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x7Decl, x7Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x8Decl, x8Ref);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReferences(tree, "x9").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl, x9Ref);
        }

        [Fact]
        public void Scope_Do_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        do
        {
            Dummy(x1);
        }
        while (TakeOutParam(true, out var x1) && x1);
    }

    void Test2()
    {
        do
            Dummy(x2);
        while (TakeOutParam(true, out var x2) && x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        do
            Dummy(x4);
        while (TakeOutParam(true, out var x4) && x4);
    }

    void Test6()
    {
        do
            Dummy(x6);
        while (x6 && TakeOutParam(true, out var x6));
    }

    void Test7()
    {
        do
        {
            var x7 = 12;
            Dummy(x7);
        }
        while (TakeOutParam(true, out var x7) && x7);
    }

    void Test8()
    {
        do
            Dummy(x8);
        while (TakeOutParam(true, out var x8) && x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        do
        {   
            Dummy(x9);
            do
                Dummy(x9);
            while (TakeOutParam(true, out var x9) && x9); // 2
        }
        while (TakeOutParam(true, out var x9) && x9);
    }

    void Test10()
    {
        do
        {   
            var y10 = 12;
            Dummy(y10);
        }
        while (TakeOutParam(y10, out var x10));
    }

    //void Test11()
    //{
    //    do
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //    while (TakeOutParam(y11, out var x11));
    //}

    void Test12()
    {
        do
            var y12 = 12;
        while (TakeOutParam(y12, out var x12));
    }

    //void Test13()
    //{
    //    do
    //        let y13 = 12;
    //    while (TakeOutParam(y13, out var x13));
    //}

    void Test14()
    {
        do
        {
            Dummy(x14);
        }
        while (Dummy(TakeOutParam(1, out var x14), 
                     TakeOutParam(2, out var x14), 
                     x14));
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (97,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(97, 13),
                // (14,19): error CS0841: Cannot use local variable 'x1' before it is declared
                //             Dummy(x1);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(14, 19),
                // (22,19): error CS0841: Cannot use local variable 'x2' before it is declared
                //             Dummy(x2);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x2").WithArguments("x2").WithLocation(22, 19),
                // (33,43): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         while (TakeOutParam(true, out var x4) && x4);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(33, 43),
                // (32,19): error CS0841: Cannot use local variable 'x4' before it is declared
                //             Dummy(x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(32, 19),
                // (40,16): error CS0841: Cannot use local variable 'x6' before it is declared
                //         while (x6 && TakeOutParam(true, out var x6));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(40, 16),
                // (39,19): error CS0841: Cannot use local variable 'x6' before it is declared
                //             Dummy(x6);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(39, 19),
                // (47,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(47, 17),
                // (56,19): error CS0841: Cannot use local variable 'x8' before it is declared
                //             Dummy(x8);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x8").WithArguments("x8").WithLocation(56, 19),
                // (59,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(59, 34),
                // (66,19): error CS0841: Cannot use local variable 'x9' before it is declared
                //             Dummy(x9);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x9").WithArguments("x9").WithLocation(66, 19),
                // (69,47): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             while (TakeOutParam(true, out var x9) && x9); // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(69, 47),
                // (68,23): error CS0841: Cannot use local variable 'x9' before it is declared
                //                 Dummy(x9);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x9").WithArguments("x9").WithLocation(68, 23),
                // (81,29): error CS0103: The name 'y10' does not exist in the current context
                //         while (TakeOutParam(y10, out var x10));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(81, 29),
                // (98,29): error CS0103: The name 'y12' does not exist in the current context
                //         while (TakeOutParam(y12, out var x12));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(98, 29),
                // (97,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(97, 17),
                // (115,46): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                      TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(115, 46),
                // (112,19): error CS0841: Cannot use local variable 'x14' before it is declared
                //             Dummy(x14);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x14").WithArguments("x14").WithLocation(112, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[1]);
            VerifyNotAnOutLocal(model, x7Ref[0]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[1], x9Ref[2]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[0], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[1]);
            VerifyNotAnOutLocal(model, y10Ref[0]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_Do_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        if (true)
            do
            {
            }
            while (TakeOutParam(true, out var x1));

        x1++;
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (18,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(18, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl);
            VerifyNotInScope(model, x1Ref);
        }

        [Fact]
        public void Scope_Do_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (DoStatementSyntax)SyntaxFactory.ParseStatement(@"
do {} while (Dummy(TakeOutParam(true, out var x1), x1));
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Do_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        int f = 1;

        do
        {
            ;
        }
        while (Dummy(f < 3, TakeOutParam(f++, out var x1), x1));
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
2
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Do_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f;

        do
        {
            f = false;
        }
        while (Dummy(f, TakeOutParam((f ? 1 : 2), out int x1), x1));
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Do_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        if (f)        
            do
                ;
            while (Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1) && false);

        if (f)        
        {
            do
                ;
            while (Dummy(f, TakeOutParam((f ? 3 : 4), out var x1), x1) && false);
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void Do_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        int f = 1;
        var l = new System.Collections.Generic.List<System.Action>();

        do
        {
            ;
        }
        while (Dummy(f < 3, TakeOutParam(f++, out var x1), x1, l, () => System.Console.WriteLine(x1)));

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static bool Dummy(bool x, object y, object z, System.Collections.Generic.List<System.Action> l, System.Action d) 
    {
        l.Add(d);
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
2
3
--
1
2
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Scope_ExpressionBodiedFunctions_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Test3(object o) => TakeOutParam(o, out int x3) && x3 > 0;

    bool Test4(object o) => x4 && TakeOutParam(o, out int x4);

    bool Test5(object o1, object o2) => TakeOutParam(o1, out int x5) && 
                                         TakeOutParam(o2, out int x5) && 
                                         x5 > 0;

    bool Test61 (object o) => TakeOutParam(o, out int x6) && x6 > 0; bool Test62 (object o) => TakeOutParam(o, out int x6) && x6 > 0;

    bool Test71(object o) => TakeOutParam(o, out int x7) && x7 > 0; 
    void Test72() => Dummy(x7, 2); 
    void Test73() { Dummy(x7, 3); } 

    bool Test11(object x11) => TakeOutParam(1, out int x11) && 
                             x11 > 0;

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (10,29): error CS0841: Cannot use local variable 'x4' before it is declared
                //     bool Test4(object o) => x4 && TakeOutParam(o, out int x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(10, 29),
                // (13,67): error CS0128: A local variable named 'x5' is already defined in this scope
                //                                          TakeOutParam(o2, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(13, 67),
                // (19,28): error CS0103: The name 'x7' does not exist in the current context
                //     void Test72() => Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(19, 28),
                // (20,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(20, 27),
                // (22,56): error CS0136: A local or parameter named 'x11' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     bool Test11(object x11) => TakeOutParam(1, out int x11) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x11").WithArguments("x11").WithLocation(22, 56)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").Single();
            VerifyModelForOutVar(model, x11Decl, x11Ref);
        }

        [Fact]
        public void ExpressionBodiedFunctions_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static bool Test1() => TakeOutParam(1, out int x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");
        }

        [Fact]
        public void ExpressionBodiedFunctions_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static bool Test1() => TakeOutParam(1, out var x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");
        }

        [Fact]
        [WorkItem(14214, "https://github.com/dotnet/roslyn/issues/14214")]
        public void Scope_ExpressionBodiedLocalFunctions_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test3()
    {
        bool f (object o) => TakeOutParam(o, out int x3) && x3 > 0;
        f(null);
    }

    void Test4()
    {
        bool f (object o) => x4 && TakeOutParam(o, out int x4);
        f(null);
    }

    void Test5()
    {
        bool f (object o1, object o2) => TakeOutParam(o1, out int x5) && 
                                         TakeOutParam(o2, out int x5) && 
                                         x5 > 0;
        f(null, null);
    }

    void Test6()
    {
        bool f1 (object o) => TakeOutParam(o, out int x6) && x6 > 0; bool f2 (object o) => TakeOutParam(o, out int x6) && x6 > 0;
        f1(null);
        f2(null);
    }

    void Test7()
    {
        Dummy(x7, 1);
         
        bool f (object o) => TakeOutParam(o, out int x7) && x7 > 0; 

        Dummy(x7, 2); 
        f(null);
    }

    void Test11()
    {
        var x11 = 11;
        Dummy(x11);
        bool f (object o) => TakeOutParam(o, out int x11) && 
                             x11 > 0;
        f(null);
    }

    void Test12()
    {
        bool f (object o) => TakeOutParam(o, out int x12) && 
                             x12 > 0;
        var x12 = 11;
        Dummy(x12);
        f(null);
    }

    System.Action Test13()
    {
        return () =>
                    {
                        bool f (object o) => TakeOutParam(o, out int x13) && x13 > 0;
                        f(null);
                    };
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (18,30): error CS0841: Cannot use local variable 'x4' before it is declared
                //         bool f (object o) => x4 && TakeOutParam(o, out int x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(18, 30),
                // (25,67): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                                          TakeOutParam(o2, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(25, 67),
                // (39,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(39, 15),
                // (43,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(43, 15)
                );

            compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_3);
            compilation.VerifyDiagnostics(
                // (18,30): error CS0841: Cannot use local variable 'x4' before it is declared
                //         bool f (object o) => x4 && TakeOutParam(o, out int x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(18, 30),
                // (25,67): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                                          TakeOutParam(o2, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(25, 67),
                // (39,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(39, 15),
                // (43,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(43, 15),
                // (51,54): error CS0136: A local or parameter named 'x11' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         bool f (object o) => TakeOutParam(o, out int x11) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x11").WithArguments("x11").WithLocation(51, 54),
                // (58,54): error CS0136: A local or parameter named 'x12' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         bool f (object o) => TakeOutParam(o, out int x12) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x12").WithArguments("x12").WithLocation(58, 54)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            // Data flow for the following disabled due to https://github.com/dotnet/roslyn/issues/14214

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();

            VerifyModelForOutVarWithoutDataFlow(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyNotInScope(model, x7Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x7Decl, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(2, x11Ref.Length);
            VerifyNotAnOutLocal(model, x11Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x11Decl, x11Ref[1]);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(2, x12Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x12Decl, x12Ref[0]);
            VerifyNotAnOutLocal(model, x12Ref[1]);

            var x13Decl = GetOutVarDeclarations(tree, "x13").Single();
            var x13Ref = GetReferences(tree, "x13").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x13Decl, x13Ref);
        }

        [Fact]
        public void ExpressionBodiedLocalFunctions_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static bool Test1()
    {
        bool f() =>  TakeOutParam(1, out int x1) && Dummy(x1); 
        return f();
    }

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");
        }

        [Fact]
        public void ExpressionBodiedLocalFunctions_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static bool Test1()
    {
        bool f() =>  TakeOutParam(1, out var x1) && Dummy(x1); 
        return f();
    }

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");
        }

        [Fact]
        public void Scope_ExpressionBodiedProperties_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Test3 => TakeOutParam(3, out int x3) && x3 > 0;

    bool Test4 => x4 && TakeOutParam(4, out int x4);

    bool Test5 => TakeOutParam(51, out int x5) && 
                  TakeOutParam(52, out int x5) && 
                  x5 > 0;

    bool Test61 => TakeOutParam(6, out int x6) && x6 > 0; bool Test62 => TakeOutParam(6, out int x6) && x6 > 0;

    bool Test71 => TakeOutParam(7, out int x7) && x7 > 0; 
    bool Test72 => Dummy(x7, 2); 
    void Test73() { Dummy(x7, 3); } 

    bool this[object x11] => TakeOutParam(1, out int x11) && 
                             x11 > 0;

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (10,19): error CS0841: Cannot use local variable 'x4' before it is declared
                //     bool Test4 => x4 && TakeOutParam(4, out int x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(10, 19),
                // (13,44): error CS0128: A local variable named 'x5' is already defined in this scope
                //                   TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(13, 44),
                // (19,26): error CS0103: The name 'x7' does not exist in the current context
                //     bool Test72 => Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(19, 26),
                // (20,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(20, 27),
                // (22,54): error CS0136: A local or parameter named 'x11' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     bool this[object x11] => TakeOutParam(1, out int x11) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x11").WithArguments("x11").WithLocation(22, 54)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").Single();
            VerifyModelForOutVar(model, x11Decl, x11Ref);
        }

        [Fact]
        public void ExpressionBodiedProperties_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1);
        System.Console.WriteLine(new X()[0]);
    }

    static bool Test1 => TakeOutParam(2, out int x1) && Dummy(x1); 

    bool this[object x] => TakeOutParam(1, out int x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"2
True
1
True");
        }

        [Fact]
        public void ExpressionBodiedProperties_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1);
        System.Console.WriteLine(new X()[0]);
    }

    static bool Test1 => TakeOutParam(2, out var x1) && Dummy(x1); 

    bool this[object x] => TakeOutParam(1, out var x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"2
True
1
True");
        }

        [Fact]
        public void Scope_ExpressionStatement_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        Dummy(TakeOutParam(true, out var x1), x1);
        {
            Dummy(TakeOutParam(true, out var x1), x1);
        }
        Dummy(TakeOutParam(true, out var x1), x1);
    }

    void Test2()
    {
        Dummy(x2, TakeOutParam(true, out var x2));
    }

    void Test3(int x3)
    {
        Dummy(TakeOutParam(true, out var x3), x3);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);
        Dummy(TakeOutParam(true, out var x4), x4);
    }

    void Test5()
    {
        Dummy(TakeOutParam(true, out var x5), x5);
        var x5 = 11;
        Dummy(x5);
    }

    //void Test6()
    //{
    //    let x6 = 11;
    //    Dummy(x6);
    //    Dummy(TakeOutParam(true, out var x6), x6);
    //}

    //void Test7()
    //{
    //    Dummy(TakeOutParam(true, out var x7), x7);
    //    let x7 = 11;
    //    Dummy(x7);
    //}

    void Test8()
    {
        Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
    }

    void Test9(bool y9)
    {
        if (y9)
            Dummy(TakeOutParam(true, out var x9), x9);
    }

    System.Action Test10(bool y10)
    {
        return () =>
                {
                    if (y10)
                        Dummy(TakeOutParam(true, out var x10), x10);
                };
    }

    void Test11()
    {
        Dummy(x11);
        Dummy(TakeOutParam(true, out var x11), x11);
    }

    void Test12()
    {
        Dummy(TakeOutParam(true, out var x12), x12);
        Dummy(x12);
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (14,46): error CS0136: A local or parameter named 'x1' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x1").WithArguments("x1").WithLocation(14, 46),
                // (16,42): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //         Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(16, 42),
                // (21,15): error CS0841: Cannot use local variable 'x2' before it is declared
                //         Dummy(x2, TakeOutParam(true, out var x2));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x2").WithArguments("x2").WithLocation(21, 15),
                // (26,42): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         Dummy(TakeOutParam(true, out var x3), x3);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(26, 42),
                // (33,42): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //         Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(33, 42),
                // (39,13): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //         var x5 = 11;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(39, 13),
                // (39,13): warning CS0219: The variable 'x5' is assigned but its value is never used
                //         var x5 = 11;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x5").WithArguments("x5").WithLocation(39, 13),
                // (59,79): error CS0128: A local variable or function named 'x8' is already defined in this scope
                //         Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(59, 79),
                // (79,15): error CS0841: Cannot use local variable 'x11' before it is declared
                //         Dummy(x11);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x11").WithArguments("x11").WithLocation(79, 15)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl[2]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(2, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Decl.Length);
            Assert.Equal(2, x8Ref.Length);
            for (int i = 0; i < x8Decl.Length; i++)
            {
                VerifyModelForOutVar(model, x8Decl[0], x8Ref[i]);
            }
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl[1]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReferences(tree, "x9").Single();
            VerifyModelForOutVar(model, x9Decl, x9Ref);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            VerifyModelForOutVar(model, x10Decl, x10Ref);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(2, x11Ref.Length);
            VerifyModelForOutVar(model, x11Decl, x11Ref);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(2, x12Ref.Length);
            VerifyModelForOutVar(model, x12Decl, x12Ref);
        }

        [Fact]
        public void Scope_ExpressionStatement_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test0();
    }

    static object Test0()
    {
        bool test = true;

        if (test)
            Test2(Test1(out int x1), x1);

        if (test)
        {
            Test2(Test1(out int x1), x1);
        }

        return null;
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }

    static object Test2(object x, object y)
    {
        System.Console.Write(y);
        return x;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: "11").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void Scope_ExpressionStatement_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        if (true)
            Dummy(TakeOutParam(true, out var x1));

        x1++;
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (15,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(15, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0]);
            VerifyNotInScope(model, x1Ref[0]);
        }

        [Fact]
        public void Scope_ExpressionStatement_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (ExpressionStatementSyntax)SyntaxFactory.ParseStatement(@"
Dummy(TakeOutParam(true, out var x1), x1);
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_FieldInitializers_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Test3 = TakeOutParam(3, out int x3) && x3 > 0;

    bool Test4 = x4 && TakeOutParam(4, out int x4);

    bool Test5 = TakeOutParam(51, out int x5) && 
                 TakeOutParam(52, out int x5) && 
                 x5 > 0;

    bool Test61 = TakeOutParam(6, out int x6) && x6 > 0, Test62 = TakeOutParam(6, out int x6) && x6 > 0;

    bool Test71 = TakeOutParam(7, out int x7) && x7 > 0; 
    bool Test72 = Dummy(x7, 2); 
    void Test73() { Dummy(x7, 3); } 

    bool Test81 = TakeOutParam(8, out int x8), Test82 = x8 > 0;
    bool Test91 = x9 > 0, Test92 = TakeOutParam(9, out int x9);

    bool Dummy(params object[] x) {return true;}
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (10,18): error CS0841: Cannot use local variable 'x4' before it is declared
                //     bool Test4 = x4 && TakeOutParam(4, out int x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(10, 18),
                // (13,43): error CS0128: A local variable named 'x5' is already defined in this scope
                //                  TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(13, 43),
                // (19,25): error CS0103: The name 'x7' does not exist in the current context
                //     bool Test72 = Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(19, 25),
                // (20,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(20, 27),
                // (22,57): error CS0103: The name 'x8' does not exist in the current context
                //     bool Test81 = TakeOutParam(8, out int x8), Test82 = x8 > 0;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(22, 57),
                // (23,19): error CS0103: The name 'x9' does not exist in the current context
                //     bool Test91 = x9 > 0, Test92 = TakeOutParam(9, out int x9);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x9").WithArguments("x9").WithLocation(23, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReference(tree, "x8");
            VerifyModelForOutVar(model, x8Decl);
            VerifyNotInScope(model, x8Ref);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReference(tree, "x9");
            VerifyNotInScope(model, x9Ref);
            VerifyModelForOutVar(model, x9Decl);
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void Scope_FieldInitializers_02()
        {
            var source =
@"using static Test;
public enum X
{
    Test3 = TakeOutParam(3, out int x3) ? x3 : 0,

    Test4 = x4 && TakeOutParam(4, out int x4) ? 1 : 0,

    Test5 = TakeOutParam(51, out int x5) && 
            TakeOutParam(52, out int x5) && 
            x5 > 0 ? 1 : 0,

    Test61 = TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0, Test62 = TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0,

    Test71 = TakeOutParam(7, out int x7) && x7 > 0 ? 1 : 0, 
    Test72 = x7, 
}

class Test
{
    public static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugDll, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (6,13): error CS0841: Cannot use local variable 'x4' before it is declared
                //     Test4 = x4 && TakeOutParam(4, out int x4) ? 1 : 0,
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(6, 13),
                // (9,38): error CS0128: A local variable named 'x5' is already defined in this scope
                //             TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(9, 38),
                // (8,13): error CS0133: The expression being assigned to 'X.Test5' must be constant
                //     Test5 = TakeOutParam(51, out int x5) && 
                Diagnostic(ErrorCode.ERR_NotConstantExpression, @"TakeOutParam(51, out int x5) && 
            TakeOutParam(52, out int x5) && 
            x5 > 0 ? 1 : 0").WithArguments("X.Test5").WithLocation(8, 13),
                // (12,14): error CS0133: The expression being assigned to 'X.Test61' must be constant
                //     Test61 = TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0, Test62 = TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0,
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0").WithArguments("X.Test61").WithLocation(12, 14),
                // (12,70): error CS0133: The expression being assigned to 'X.Test62' must be constant
                //     Test61 = TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0, Test62 = TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0,
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(6, out int x6) && x6 > 0 ? 1 : 0").WithArguments("X.Test62").WithLocation(12, 70),
                // (14,14): error CS0133: The expression being assigned to 'X.Test71' must be constant
                //     Test71 = TakeOutParam(7, out int x7) && x7 > 0 ? 1 : 0, 
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(7, out int x7) && x7 > 0 ? 1 : 0").WithArguments("X.Test71").WithLocation(14, 14),
                // (15,14): error CS0103: The name 'x7' does not exist in the current context
                //     Test72 = x7, 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(15, 14),
                // (4,13): error CS0133: The expression being assigned to 'X.Test3' must be constant
                //     Test3 = TakeOutParam(3, out int x3) ? x3 : 0,
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(3, out int x3) ? x3 : 0").WithArguments("X.Test3").WithLocation(4, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);

            var node = tree.GetRoot().DescendantNodes().OfType<EqualsValueClauseSyntax>().First();

            compilation.VerifyOperationTree(node, expectedOperationTree:
@"
IFieldInitializerOperation (Field: X.Test3) (OperationKind.FieldInitializer, Type: null, IsInvalid) (Syntax: '= TakeOutPa ... 3) ? x3 : 0')
  Locals: Local_1: System.Int32 x3
  IConditionalOperation (OperationKind.Conditional, Type: System.Int32, IsInvalid) (Syntax: 'TakeOutPara ... 3) ? x3 : 0')
    Condition: 
      IInvocationOperation (System.Boolean Test.TakeOutParam(System.Object y, out System.Int32 x)) (OperationKind.Invocation, Type: System.Boolean, IsInvalid) (Syntax: 'TakeOutPara ... out int x3)')
        Instance Receiver: 
          null
        Arguments(2):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: y) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: '3')
              IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Object, IsInvalid, IsImplicit) (Syntax: '3')
                Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                Operand: 
                  ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 3, IsInvalid) (Syntax: '3')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out int x3')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'int x3')
                ILocalReferenceOperation: x3 (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x3')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
    WhenTrue: 
      ILocalReferenceOperation: x3 (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x3')
    WhenFalse: 
      ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 0, IsInvalid) (Syntax: '0')
");
        }

        [Fact]
        public void Scope_FieldInitializers_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    const bool Test3 = TakeOutParam(3, out int x3) && x3 > 0;

    const bool Test4 = x4 && TakeOutParam(4, out int x4);

    const bool Test5 = TakeOutParam(51, out int x5) && 
                       TakeOutParam(52, out int x5) && 
                       x5 > 0;

    const bool Test61 = TakeOutParam(6, out int x6) && x6 > 0, Test62 = TakeOutParam(6, out int x6) && x6 > 0;

    const bool Test71 = TakeOutParam(7, out int x7) && x7 > 0; 
    const bool Test72 = x7 > 2; 
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,24): error CS0133: The expression being assigned to 'X.Test3' must be constant
                //     const bool Test3 = TakeOutParam(3, out int x3) && x3 > 0;
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(3, out int x3) && x3 > 0").WithArguments("X.Test3").WithLocation(8, 24),
                // (10,24): error CS0841: Cannot use local variable 'x4' before it is declared
                //     const bool Test4 = x4 && TakeOutParam(4, out int x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(10, 24),
                // (13,49): error CS0128: A local variable named 'x5' is already defined in this scope
                //                        TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(13, 49),
                // (12,24): error CS0133: The expression being assigned to 'X.Test5' must be constant
                //     const bool Test5 = TakeOutParam(51, out int x5) && 
                Diagnostic(ErrorCode.ERR_NotConstantExpression, @"TakeOutParam(51, out int x5) && 
                       TakeOutParam(52, out int x5) && 
                       x5 > 0").WithArguments("X.Test5").WithLocation(12, 24),
                // (16,25): error CS0133: The expression being assigned to 'X.Test61' must be constant
                //     const bool Test61 = TakeOutParam(6, out int x6) && x6 > 0, Test62 = TakeOutParam(6, out int x6) && x6 > 0;
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(6, out int x6) && x6 > 0").WithArguments("X.Test61").WithLocation(16, 25),
                // (16,73): error CS0133: The expression being assigned to 'X.Test62' must be constant
                //     const bool Test61 = TakeOutParam(6, out int x6) && x6 > 0, Test62 = TakeOutParam(6, out int x6) && x6 > 0;
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(6, out int x6) && x6 > 0").WithArguments("X.Test62").WithLocation(16, 73),
                // (18,25): error CS0133: The expression being assigned to 'X.Test71' must be constant
                //     const bool Test71 = TakeOutParam(7, out int x7) && x7 > 0; 
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "TakeOutParam(7, out int x7) && x7 > 0").WithArguments("X.Test71").WithLocation(18, 25),
                // (19,25): error CS0103: The name 'x7' does not exist in the current context
                //     const bool Test72 = x7 > 2; 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(19, 25),
                // (20,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(20, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_FieldInitializers_04()
        {
            var source =
@"
class X : Y
{
    public static void Main()
    {
    }

    bool Test3 = TakeOutParam(out int x3, x3);

    bool Test4 = TakeOutParam(out var x4, x4);

    bool Test5 = TakeOutParam(out int x5, 5);

    X()
    : this(x5)
    {
        System.Console.WriteLine(x5);
    }

    X(object x) 
    : base(x5) 
    => System.Console.WriteLine(x5);

    static bool Test6 = TakeOutParam(out int x6, 6);
    static X()
    {
        System.Console.WriteLine(x6);
    }

    static bool TakeOutParam(out int x, int y) 
    {
        x = 123;
        return true;
    }
}

class Y
{
    public Y(object y) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,43): error CS0165: Use of unassigned local variable 'x3'
                //     bool Test3 = TakeOutParam(out int x3, x3);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x3").WithArguments("x3").WithLocation(8, 43),
                // (10,43): error CS8196: Reference to an implicitly-typed out variable 'x4' is not permitted in this location.
                //     bool Test4 = TakeOutParam(out var x4, x4);
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableUsedInForbiddenZone, "x4").WithArguments("x4").WithLocation(10, 43),
                // (15,12): error CS0103: The name 'x5' does not exist in the current context
                //     : this(x5)
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(15, 12),
                // (17,34): error CS0103: The name 'x5' does not exist in the current context
                //         System.Console.WriteLine(x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(17, 34),
                // (21,12): error CS0103: The name 'x5' does not exist in the current context
                //     : base(x5) 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(21, 12),
                // (22,33): error CS0103: The name 'x5' does not exist in the current context
                //     => System.Console.WriteLine(x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(22, 33),
                // (27,34): error CS0103: The name 'x6' does not exist in the current context
                //         System.Console.WriteLine(x6);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x6").WithArguments("x6").WithLocation(27, 34)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(4, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl);
            VerifyNotInScope(model, x5Ref[0]);
            VerifyNotInScope(model, x5Ref[1]);
            VerifyNotInScope(model, x5Ref[2]);
            VerifyNotInScope(model, x5Ref[3]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            VerifyModelForOutVar(model, x6Decl);
            VerifyNotInScope(model, x6Ref);
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void FieldInitializers_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1);
    }

    static bool Test1 = TakeOutParam(1, out int x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");

            CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_2).VerifyDiagnostics(
                // (9,45): error CS8320: Feature 'declaration of expression variables in member initializers and queries' is not available in C# 7.2. Please use language version 7.3 or greater.
                //     static bool Test1 = TakeOutParam(1, out int x1) && Dummy(x1); 
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion7_2, "int x1").WithArguments("declaration of expression variables in member initializers and queries", "7.3").WithLocation(9, 45)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var node = tree.GetRoot().DescendantNodes().OfType<EqualsValueClauseSyntax>().Single();

            compilation.VerifyOperationTree(node, expectedOperationTree:
@"
IFieldInitializerOperation (Field: System.Boolean X.Test1) (OperationKind.FieldInitializer, Type: null) (Syntax: '= TakeOutPa ... & Dummy(x1)')
  Locals: Local_1: System.Int32 x1
  IBinaryOperation (BinaryOperatorKind.ConditionalAnd) (OperationKind.Binary, Type: System.Boolean) (Syntax: 'TakeOutPara ... & Dummy(x1)')
    Left: 
      IInvocationOperation (System.Boolean X.TakeOutParam(System.Int32 y, out System.Int32 x)) (OperationKind.Invocation, Type: System.Boolean) (Syntax: 'TakeOutPara ... out int x1)')
        Instance Receiver: 
          null
        Arguments(2):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: y) (OperationKind.Argument, Type: null) (Syntax: '1')
              ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 1) (Syntax: '1')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null) (Syntax: 'out int x1')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32) (Syntax: 'int x1')
                ILocalReferenceOperation: x1 (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x1')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
    Right: 
      IInvocationOperation (System.Boolean X.Dummy(System.Int32 x)) (OperationKind.Invocation, Type: System.Boolean) (Syntax: 'Dummy(x1)')
        Instance Receiver: 
          null
        Arguments(1):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null) (Syntax: 'x1')
              ILocalReferenceOperation: x1 (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x1')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
        }

        [Fact]
        [WorkItem(10487, "https://github.com/dotnet/roslyn/issues/10487")]
        public void FieldInitializers_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1);
    }

    static bool Test1 = TakeOutParam(1, out int x1) && Dummy(() => x1); 

    static bool Dummy(System.Func<int> x) 
    {
        System.Console.WriteLine(x());
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");
        }

        [Fact]
        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
        public void FieldInitializers_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static System.Func<bool> Test1 = () => TakeOutParam(1, out int x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");
        }

        [Fact]
        public void FieldInitializers_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }
    static bool a = false;
    bool Test1 = a && TakeOutParam(3, out int x1) || x1 > 0;
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,54): error CS0165: Use of unassigned local variable 'x1'
                //     bool Test1 = a && TakeOutParam(3, out int x1) || x1 > 0;
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(8, 54)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void FieldInitializers_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1);
    }

    static int Test1 = TakeOutParam(1, out var x1) ? Test2(((System.Func<int>)(() => x1++))(), ref x1) : -1; 

    static int Test2(object a, ref int x)
    {
        System.Console.WriteLine(x);
        x++;
        return x;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"2
3");
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Equal("System.Int32", ((ILocalSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(GetVariableDesignation(x1Decl))).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_Fixed_01()
        {
            var source =
@"
public unsafe class X
{
    public static void Main()
    {
    }

    int[] Dummy(params object[] x) {return null;}

    void Test1()
    {
        fixed (int* p = Dummy(TakeOutParam(true, out var x1) && x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        fixed (int* p = Dummy(TakeOutParam(true, out var x2) && x2))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        fixed (int* p = Dummy(TakeOutParam(true, out var x4) && x4))
            Dummy(x4);
    }

    void Test6()
    {
        fixed (int* p = Dummy(x6 && TakeOutParam(true, out var x6)))
            Dummy(x6);
    }

    void Test7()
    {
        fixed (int* p = Dummy(TakeOutParam(true, out var x7) && x7))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        fixed (int* p = Dummy(TakeOutParam(true, out var x8) && x8))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        fixed (int* p1 = Dummy(TakeOutParam(true, out var x9) && x9))
        {   
            Dummy(x9);
            fixed (int* p2 = Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        fixed (int* p = Dummy(TakeOutParam(y10, out var x10)))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    fixed (int* p = Dummy(TakeOutParam(y11, out var x11)))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        fixed (int* p = Dummy(TakeOutParam(y12, out var x12)))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    fixed (int* p = Dummy(TakeOutParam(y13, out var x13)))
    //        let y13 = 12;
    //}

    void Test14()
    {
        fixed (int* p = Dummy(TakeOutParam(1, out var x14), 
                              TakeOutParam(2, out var x14), 
                              x14))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,58): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         fixed (int* p = Dummy(TakeOutParam(true, out var x4) && x4))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 58),
                // (35,31): error CS0841: Cannot use local variable 'x6' before it is declared
                //         fixed (int* p = Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 31),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,63): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             fixed (int* p2 = Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 63),
                // (68,44): error CS0103: The name 'y10' does not exist in the current context
                //         fixed (int* p = Dummy(TakeOutParam(y10, out var x10)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 44),
                // (86,44): error CS0103: The name 'y12' does not exist in the current context
                //         fixed (int* p = Dummy(TakeOutParam(y12, out var x12)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 44),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,55): error CS0128: A local variable named 'x14' is already defined in this scope
                //                               TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 55)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_Fixed_02()
        {
            var source =
@"
public unsafe class X
{
    public static void Main()
    {
    }

    int[] Dummy(params object[] x) {return null;}
    int[] Dummy(int* x) {return null;}

    void Test1()
    {
        fixed (int* x1 = 
                         Dummy(TakeOutParam(true, out var x1) && x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        fixed (int* p = Dummy(TakeOutParam(true, out var x2) && x2),
                    x2 = Dummy())
        {
            Dummy(x2);
        }
    }

    void Test3()
    {
        fixed (int* x3 = Dummy(),
                    p = Dummy(TakeOutParam(true, out var x3) && x3))
        {
            Dummy(x3);
        }
    }

    void Test4()
    {
        fixed (int* p1 = Dummy(TakeOutParam(true, out var x4) && x4),
                    p2 = Dummy(TakeOutParam(true, out var x4) && x4))
        {
            Dummy(x4);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (14,59): error CS0128: A local variable named 'x1' is already defined in this scope
                //                          Dummy(TakeOutParam(true, out var x1) && x1))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(14, 59),
                // (14,32): error CS0019: Operator '&&' cannot be applied to operands of type 'bool' and 'int*'
                //                          Dummy(TakeOutParam(true, out var x1) && x1))
                Diagnostic(ErrorCode.ERR_BadBinaryOps, "TakeOutParam(true, out var x1) && x1").WithArguments("&&", "bool", "int*").WithLocation(14, 32),
                // (14,66): error CS0165: Use of unassigned local variable 'x1'
                //                          Dummy(TakeOutParam(true, out var x1) && x1))
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(14, 66),
                // (23,21): error CS0128: A local variable named 'x2' is already defined in this scope
                //                     x2 = Dummy())
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(23, 21),
                // (32,58): error CS0128: A local variable named 'x3' is already defined in this scope
                //                     p = Dummy(TakeOutParam(true, out var x3) && x3))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(32, 58),
                // (32,31): error CS0019: Operator '&&' cannot be applied to operands of type 'bool' and 'int*'
                //                     p = Dummy(TakeOutParam(true, out var x3) && x3))
                Diagnostic(ErrorCode.ERR_BadBinaryOps, "TakeOutParam(true, out var x3) && x3").WithArguments("&&", "bool", "int*").WithLocation(32, 31),
                // (41,59): error CS0128: A local variable named 'x4' is already defined in this scope
                //                     p2 = Dummy(TakeOutParam(true, out var x4) && x4))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(41, 59)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x3Decl);
            VerifyNotAnOutLocal(model, x3Ref[0]);
            VerifyNotAnOutLocal(model, x3Ref[1]);

            var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Decl.Length);
            Assert.Equal(3, x4Ref.Length);
            VerifyModelForOutVar(model, x4Decl[0], x4Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
        }

        [Fact]
        public void Fixed_01()
        {
            var source =
@"
public unsafe class X
{
    public static void Main()
    {
        fixed (int* p = Dummy(TakeOutParam(""fixed"", out var x1), x1))
        {
            System.Console.WriteLine(x1);
        }
    }

    static int[] Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new int[1];
    }

    static bool TakeOutParam(string y, out string x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, verify: Verification.Fails, expectedOutput:
@"fixed
fixed");
        }

        [Fact]
        public void Fixed_02()
        {
            var source =
@"
public unsafe class X
{
    public static void Main()
    {
        fixed (int* p = Dummy(TakeOutParam(""fixed"", out string x1), x1))
        {
            System.Console.WriteLine(x1);
        }
    }

    static int[] Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new int[1];
    }

    static bool TakeOutParam(string y, out string x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, verify: Verification.Fails, expectedOutput:
@"fixed
fixed");
        }

        [Fact]
        public void Scope_For_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (
             Dummy(TakeOutParam(true, out var x1) && x1)
             ;;)
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        for (
             Dummy(TakeOutParam(true, out var x2) && x2)
             ;;)
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        for (
             Dummy(TakeOutParam(true, out var x4) && x4)
             ;;)
            Dummy(x4);
    }

    void Test6()
    {
        for (
             Dummy(x6 && TakeOutParam(true, out var x6))
             ;;)
            Dummy(x6);
    }

    void Test7()
    {
        for (
             Dummy(TakeOutParam(true, out var x7) && x7)
             ;;)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        for (
             Dummy(TakeOutParam(true, out var x8) && x8)
             ;;)
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        for (
             Dummy(TakeOutParam(true, out var x9) && x9)
             ;;)
        {   
            Dummy(x9);
            for (
                 Dummy(TakeOutParam(true, out var x9) && x9) // 2
                 ;;)
                Dummy(x9);
        }
    }

    void Test10()
    {
        for (
             Dummy(TakeOutParam(y10, out var x10))
             ;;)
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    for (
    //         Dummy(TakeOutParam(y11, out var x11))
    //         ;;)
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        for (
             Dummy(TakeOutParam(y12, out var x12))
             ;;)
            var y12 = 12;
    }

    //void Test13()
    //{
    //    for (
    //         Dummy(TakeOutParam(y13, out var x13))
    //         ;;)
    //        let y13 = 12;
    //}

    void Test14()
    {
        for (
             Dummy(TakeOutParam(1, out var x14), 
                   TakeOutParam(2, out var x14), 
                   x14)
             ;;)
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (109,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(109, 13),
                // (34,47): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(34, 47),
                // (42,20): error CS0841: Cannot use local variable 'x6' before it is declared
                //              Dummy(x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(42, 20),
                // (53,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(53, 17),
                // (65,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(65, 34),
                // (65,9): warning CS0162: Unreachable code detected
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "System").WithLocation(65, 9),
                // (76,51): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                  Dummy(TakeOutParam(true, out var x9) && x9) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(76, 51),
                // (85,33): error CS0103: The name 'y10' does not exist in the current context
                //              Dummy(TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(85, 33),
                // (107,33): error CS0103: The name 'y12' does not exist in the current context
                //              Dummy(TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(107, 33),
                // (109,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(109, 17),
                // (124,44): error CS0128: A local variable named 'x14' is already defined in this scope
                //                    TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(124, 44)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_For_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (;
             Dummy(TakeOutParam(true, out var x1) && x1)
             ;)
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        for (;
             Dummy(TakeOutParam(true, out var x2) && x2)
             ;)
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        for (;
             Dummy(TakeOutParam(true, out var x4) && x4)
             ;)
            Dummy(x4);
    }

    void Test6()
    {
        for (;
             Dummy(x6 && TakeOutParam(true, out var x6))
             ;)
            Dummy(x6);
    }

    void Test7()
    {
        for (;
             Dummy(TakeOutParam(true, out var x7) && x7)
             ;)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        for (;
             Dummy(TakeOutParam(true, out var x8) && x8)
             ;)
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        for (;
             Dummy(TakeOutParam(true, out var x9) && x9)
             ;)
        {   
            Dummy(x9);
            for (;
                 Dummy(TakeOutParam(true, out var x9) && x9) // 2
                 ;)
                Dummy(x9);
        }
    }

    void Test10()
    {
        for (;
             Dummy(TakeOutParam(y10, out var x10))
             ;)
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    for (;
    //         Dummy(TakeOutParam(y11, out var x11))
    //         ;)
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        for (;
             Dummy(TakeOutParam(y12, out var x12))
             ;)
            var y12 = 12;
    }

    //void Test13()
    //{
    //    for (;
    //         Dummy(TakeOutParam(y13, out var x13))
    //         ;)
    //        let y13 = 12;
    //}

    void Test14()
    {
        for (;
             Dummy(TakeOutParam(1, out var x14), 
                   TakeOutParam(2, out var x14), 
                   x14)
             ;)
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (109,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(109, 13),
                // (34,47): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(34, 47),
                // (42,20): error CS0841: Cannot use local variable 'x6' before it is declared
                //              Dummy(x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(42, 20),
                // (53,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(53, 17),
                // (65,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(65, 34),
                // (76,51): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                  Dummy(TakeOutParam(true, out var x9) && x9) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(76, 51),
                // (85,33): error CS0103: The name 'y10' does not exist in the current context
                //              Dummy(TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(85, 33),
                // (107,33): error CS0103: The name 'y12' does not exist in the current context
                //              Dummy(TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(107, 33),
                // (109,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(109, 17),
                // (124,44): error CS0128: A local variable named 'x14' is already defined in this scope
                //                    TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(124, 44)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_For_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (;;
             Dummy(TakeOutParam(true, out var x1) && x1)
             )
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        for (;;
             Dummy(TakeOutParam(true, out var x2) && x2)
             )
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        for (;;
             Dummy(TakeOutParam(true, out var x4) && x4)
             )
            Dummy(x4);
    }

    void Test6()
    {
        for (;;
             Dummy(x6 && TakeOutParam(true, out var x6))
             )
            Dummy(x6);
    }

    void Test7()
    {
        for (;;
             Dummy(TakeOutParam(true, out var x7) && x7)
             )
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        for (;;
             Dummy(TakeOutParam(true, out var x8) && x8)
             )
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        for (;;
             Dummy(TakeOutParam(true, out var x9) && x9)
             )
        {   
            Dummy(x9);
            for (;;
                 Dummy(TakeOutParam(true, out var x9) && x9) // 2
                 )
                Dummy(x9);
        }
    }

    void Test10()
    {
        for (;;
             Dummy(TakeOutParam(y10, out var x10))
             )
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    for (;;
    //         Dummy(TakeOutParam(y11, out var x11))
    //         )
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        for (;;
             Dummy(TakeOutParam(y12, out var x12))
             )
            var y12 = 12;
    }

    //void Test13()
    //{
    //    for (;;
    //         Dummy(TakeOutParam(y13, out var x13))
    //         )
    //        let y13 = 12;
    //}

    void Test14()
    {
        for (;;
             Dummy(TakeOutParam(1, out var x14), 
                   TakeOutParam(2, out var x14), 
                   x14)
             )
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (109,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(109, 13),
                // (16,19): error CS0103: The name 'x1' does not exist in the current context
                //             Dummy(x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(16, 19),
                // (25,19): error CS0103: The name 'x2' does not exist in the current context
                //             Dummy(x2);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x2").WithArguments("x2").WithLocation(25, 19),
                // (34,47): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(34, 47),
                // (42,20): error CS0841: Cannot use local variable 'x6' before it is declared
                //              Dummy(x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(42, 20),
                // (44,19): error CS0103: The name 'x6' does not exist in the current context
                //             Dummy(x6);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x6").WithArguments("x6").WithLocation(44, 19),
                // (63,19): error CS0103: The name 'x8' does not exist in the current context
                //             Dummy(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(63, 19),
                // (65,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(65, 34),
                // (65,9): warning CS0162: Unreachable code detected
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "System").WithLocation(65, 9),
                // (74,19): error CS0103: The name 'x9' does not exist in the current context
                //             Dummy(x9);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x9").WithArguments("x9").WithLocation(74, 19),
                // (78,23): error CS0103: The name 'x9' does not exist in the current context
                //                 Dummy(x9);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x9").WithArguments("x9").WithLocation(78, 23),
                // (71,14): warning CS0162: Unreachable code detected
                //              Dummy(TakeOutParam(true, out var x9) && x9)
                Diagnostic(ErrorCode.WRN_UnreachableCode, "Dummy").WithLocation(71, 14),
                // (85,33): error CS0103: The name 'y10' does not exist in the current context
                //              Dummy(TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(85, 33),
                // (107,33): error CS0103: The name 'y12' does not exist in the current context
                //              Dummy(TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(107, 33),
                // (109,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(109, 17),
                // (124,44): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                    TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(124, 44),
                // (128,19): error CS0103: The name 'x14' does not exist in the current context
                //             Dummy(x14);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x14").WithArguments("x14").WithLocation(128, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref[0]);
            VerifyNotInScope(model, x1Ref[1]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref[0]);
            VerifyNotInScope(model, x2Ref[1]);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1]);
            VerifyNotAnOutLocal(model, x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref[0]);
            VerifyNotInScope(model, x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0]);
            VerifyNotInScope(model, x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0]);
            VerifyNotInScope(model, x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2]);
            VerifyNotInScope(model, x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref[0]);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
            VerifyNotInScope(model, x14Ref[1]);
        }

        [Fact]
        public void Scope_For_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (var b =
             Dummy(TakeOutParam(true, out var x1) && x1)
             ;;)
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        for (var b =
             Dummy(TakeOutParam(true, out var x2) && x2)
             ;;)
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        for (var b =
             Dummy(TakeOutParam(true, out var x4) && x4)
             ;;)
            Dummy(x4);
    }

    void Test6()
    {
        for (var b =
             Dummy(x6 && TakeOutParam(true, out var x6))
             ;;)
            Dummy(x6);
    }

    void Test7()
    {
        for (var b =
             Dummy(TakeOutParam(true, out var x7) && x7)
             ;;)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        for (var b =
             Dummy(TakeOutParam(true, out var x8) && x8)
             ;;)
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        for (var b1 =
             Dummy(TakeOutParam(true, out var x9) && x9)
             ;;)
        {   
            Dummy(x9);
            for (var b2 =
                 Dummy(TakeOutParam(true, out var x9) && x9) // 2
                 ;;)
                Dummy(x9);
        }
    }

    void Test10()
    {
        for (var b =
             Dummy(TakeOutParam(y10, out var x10))
             ;;)
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    for (var b =
    //         Dummy(TakeOutParam(y11, out var x11))
    //         ;;)
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        for (var b =
             Dummy(TakeOutParam(y12, out var x12))
             ;;)
            var y12 = 12;
    }

    //void Test13()
    //{
    //    for (var b =
    //         Dummy(TakeOutParam(y13, out var x13))
    //         ;;)
    //        let y13 = 12;
    //}

    void Test14()
    {
        for (var b =
             Dummy(TakeOutParam(1, out var x14), 
                   TakeOutParam(2, out var x14), 
                   x14)
             ;;)
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (109,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(109, 13),
                // (34,47): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(34, 47),
                // (42,20): error CS0841: Cannot use local variable 'x6' before it is declared
                //              Dummy(x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(42, 20),
                // (53,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(53, 17),
                // (65,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(65, 34),
                // (65,9): warning CS0162: Unreachable code detected
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "System").WithLocation(65, 9),
                // (76,51): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                  Dummy(TakeOutParam(true, out var x9) && x9) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(76, 51),
                // (85,33): error CS0103: The name 'y10' does not exist in the current context
                //              Dummy(TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(85, 33),
                // (107,33): error CS0103: The name 'y12' does not exist in the current context
                //              Dummy(TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(107, 33),
                // (109,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(109, 17),
                // (124,44): error CS0128: A local variable named 'x14' is already defined in this scope
                //                    TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(124, 44)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_For_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (bool b =
             Dummy(TakeOutParam(true, out var x1) && x1)
             ;;)
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        for (bool b =
             Dummy(TakeOutParam(true, out var x2) && x2)
             ;;)
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        for (bool b =
             Dummy(TakeOutParam(true, out var x4) && x4)
             ;;)
            Dummy(x4);
    }

    void Test6()
    {
        for (bool b =
             Dummy(x6 && TakeOutParam(true, out var x6))
             ;;)
            Dummy(x6);
    }

    void Test7()
    {
        for (bool b =
             Dummy(TakeOutParam(true, out var x7) && x7)
             ;;)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        for (bool b =
             Dummy(TakeOutParam(true, out var x8) && x8)
             ;;)
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        for (bool b1 =
             Dummy(TakeOutParam(true, out var x9) && x9)
             ;;)
        {   
            Dummy(x9);
            for (bool b2 =
                 Dummy(TakeOutParam(true, out var x9) && x9) // 2
                 ;;)
                Dummy(x9);
        }
    }

    void Test10()
    {
        for (bool b =
             Dummy(TakeOutParam(y10, out var x10))
             ;;)
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    for (bool b =
    //         Dummy(TakeOutParam(y11, out var x11))
    //         ;;)
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        for (bool b =
             Dummy(TakeOutParam(y12, out var x12))
             ;;)
            var y12 = 12;
    }

    //void Test13()
    //{
    //    for (bool b =
    //         Dummy(TakeOutParam(y13, out var x13))
    //         ;;)
    //        let y13 = 12;
    //}

    void Test14()
    {
        for (bool b =
             Dummy(TakeOutParam(1, out var x14), 
                   TakeOutParam(2, out var x14), 
                   x14)
             ;;)
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (109,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(109, 13),
                // (34,47): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(34, 47),
                // (42,20): error CS0841: Cannot use local variable 'x6' before it is declared
                //              Dummy(x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(42, 20),
                // (53,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(53, 17),
                // (65,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(65, 34),
                // (65,9): warning CS0162: Unreachable code detected
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "System").WithLocation(65, 9),
                // (76,51): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                  Dummy(TakeOutParam(true, out var x9) && x9) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(76, 51),
                // (85,33): error CS0103: The name 'y10' does not exist in the current context
                //              Dummy(TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(85, 33),
                // (107,33): error CS0103: The name 'y12' does not exist in the current context
                //              Dummy(TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(107, 33),
                // (109,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(109, 17),
                // (124,44): error CS0128: A local variable named 'x14' is already defined in this scope
                //                    TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(124, 44)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_For_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (var x1 =
             Dummy(TakeOutParam(true, out var x1) && x1)
             ;;)
        {}
    }

    void Test2()
    {
        for (var x2 = true;
             Dummy(TakeOutParam(true, out var x2) && x2)
             ;)
        {}
    }

    void Test3()
    {
        for (var x3 = true;;
             Dummy(TakeOutParam(true, out var x3) && x3)
             )
        {}
    }

    void Test4()
    {
        for (bool x4 =
             Dummy(TakeOutParam(true, out var x4) && x4)
             ;;)
        {}
    }

    void Test5()
    {
        for (bool x5 = true;
             Dummy(TakeOutParam(true, out var x5) && x5)
             ;)
        {}
    }

    void Test6()
    {
        for (bool x6 = true;;
             Dummy(TakeOutParam(true, out var x6) && x6)
             )
        {}
    }

    void Test7()
    {
        for (bool x7 = true, b =
             Dummy(TakeOutParam(true, out var x7) && x7)
             ;;)
        {}
    }

    void Test8()
    {
        for (bool b1 = Dummy(TakeOutParam(true, out var x8) && x8), 
             b2 = Dummy(TakeOutParam(true, out var x8) && x8);
             Dummy(TakeOutParam(true, out var x8) && x8);
             Dummy(TakeOutParam(true, out var x8) && x8))
        {}
    }

    void Test9()
    {
        for (bool b = x9, 
             b2 = Dummy(TakeOutParam(true, out var x9) && x9);
             Dummy(TakeOutParam(true, out var x9) && x9);
             Dummy(TakeOutParam(true, out var x9) && x9))
        {}
    }

    void Test10()
    {
        for (var b = x10;
             Dummy(TakeOutParam(true, out var x10) && x10) &&
             Dummy(TakeOutParam(true, out var x10) && x10);
             Dummy(TakeOutParam(true, out var x10) && x10))
        {}
    }

    void Test11()
    {
        for (bool b = x11;
             Dummy(TakeOutParam(true, out var x11) && x11) &&
             Dummy(TakeOutParam(true, out var x11) && x11);
             Dummy(TakeOutParam(true, out var x11) && x11))
        {}
    }

    void Test12()
    {
        for (Dummy(x12);
             Dummy(x12) &&
             Dummy(TakeOutParam(true, out var x12) && x12);
             Dummy(TakeOutParam(true, out var x12) && x12))
        {}
    }

    void Test13()
    {
        for (var b = x13;
             Dummy(x13);
             Dummy(TakeOutParam(true, out var x13) && x13),
             Dummy(TakeOutParam(true, out var x13) && x13))
        {}
    }

    void Test14()
    {
        for (bool b = x14;
             Dummy(x14);
             Dummy(TakeOutParam(true, out var x14) && x14),
             Dummy(TakeOutParam(true, out var x14) && x14))
        {}
    }

    void Test15()
    {
        for (Dummy(x15);
             Dummy(x15);
             Dummy(x15),
             Dummy(TakeOutParam(true, out var x15) && x15))
        {}
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,47): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x1) && x1)
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 47),
                // (13,54): error CS0841: Cannot use local variable 'x1' before it is declared
                //              Dummy(TakeOutParam(true, out var x1) && x1)
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(13, 54),
                // (21,47): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x2) && x2)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(21, 47),
                // (20,18): warning CS0219: The variable 'x2' is assigned but its value is never used
                //         for (var x2 = true;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x2").WithArguments("x2").WithLocation(20, 18),
                // (29,47): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x3) && x3)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(29, 47),
                // (28,18): warning CS0219: The variable 'x3' is assigned but its value is never used
                //         for (var x3 = true;;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x3").WithArguments("x3").WithLocation(28, 18),
                // (37,47): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(37, 47),
                // (37,54): error CS0165: Use of unassigned local variable 'x4'
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x4").WithArguments("x4").WithLocation(37, 54),
                // (45,47): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x5) && x5)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(45, 47),
                // (44,19): warning CS0219: The variable 'x5' is assigned but its value is never used
                //         for (bool x5 = true;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x5").WithArguments("x5").WithLocation(44, 19),
                // (53,47): error CS0136: A local or parameter named 'x6' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x6) && x6)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x6").WithArguments("x6").WithLocation(53, 47),
                // (52,19): warning CS0219: The variable 'x6' is assigned but its value is never used
                //         for (bool x6 = true;;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x6").WithArguments("x6").WithLocation(52, 19),
                // (61,47): error CS0128: A local variable or function named 'x7' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x7) && x7)
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x7").WithArguments("x7").WithLocation(61, 47),
                // (69,52): error CS0128: A local variable or function named 'x8' is already defined in this scope
                //              b2 = Dummy(TakeOutParam(true, out var x8) && x8);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(69, 52),
                // (70,47): error CS0136: A local or parameter named 'x8' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x8) && x8);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x8").WithArguments("x8").WithLocation(70, 47),
                // (71,47): error CS0136: A local or parameter named 'x8' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x8) && x8))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x8").WithArguments("x8").WithLocation(71, 47),
                // (77,23): error CS0841: Cannot use local variable 'x9' before it is declared
                //         for (bool b = x9, 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x9").WithArguments("x9").WithLocation(77, 23),
                // (79,47): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x9) && x9);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(79, 47),
                // (80,47): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x9) && x9))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(80, 47),
                // (86,22): error CS0103: The name 'x10' does not exist in the current context
                //         for (var b = x10;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x10").WithArguments("x10").WithLocation(86, 22),
                // (88,47): error CS0128: A local variable or function named 'x10' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x10) && x10);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x10").WithArguments("x10").WithLocation(88, 47),
                // (89,47): error CS0136: A local or parameter named 'x10' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x10) && x10))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x10").WithArguments("x10").WithLocation(89, 47),
                // (95,23): error CS0103: The name 'x11' does not exist in the current context
                //         for (bool b = x11;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x11").WithArguments("x11").WithLocation(95, 23),
                // (97,47): error CS0128: A local variable or function named 'x11' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x11) && x11);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x11").WithArguments("x11").WithLocation(97, 47),
                // (98,47): error CS0136: A local or parameter named 'x11' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x11) && x11))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x11").WithArguments("x11").WithLocation(98, 47),
                // (104,20): error CS0103: The name 'x12' does not exist in the current context
                //         for (Dummy(x12);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x12").WithArguments("x12").WithLocation(104, 20),
                // (105,20): error CS0841: Cannot use local variable 'x12' before it is declared
                //              Dummy(x12) &&
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x12").WithArguments("x12").WithLocation(105, 20),
                // (107,47): error CS0136: A local or parameter named 'x12' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x12) && x12))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x12").WithArguments("x12").WithLocation(107, 47),
                // (113,22): error CS0103: The name 'x13' does not exist in the current context
                //         for (var b = x13;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x13").WithArguments("x13").WithLocation(113, 22),
                // (114,20): error CS0103: The name 'x13' does not exist in the current context
                //              Dummy(x13);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x13").WithArguments("x13").WithLocation(114, 20),
                // (116,47): error CS0128: A local variable or function named 'x13' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x13) && x13))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x13").WithArguments("x13").WithLocation(116, 47),
                // (122,23): error CS0103: The name 'x14' does not exist in the current context
                //         for (bool b = x14;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x14").WithArguments("x14").WithLocation(122, 23),
                // (123,20): error CS0103: The name 'x14' does not exist in the current context
                //              Dummy(x14);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x14").WithArguments("x14").WithLocation(123, 20),
                // (125,47): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x14) && x14))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(125, 47),
                // (131,20): error CS0103: The name 'x15' does not exist in the current context
                //         for (Dummy(x15);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x15").WithArguments("x15").WithLocation(131, 20),
                // (132,20): error CS0103: The name 'x15' does not exist in the current context
                //              Dummy(x15);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x15").WithArguments("x15").WithLocation(132, 20),
                // (133,20): error CS0841: Cannot use local variable 'x15' before it is declared
                //              Dummy(x15),
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x15").WithArguments("x15").WithLocation(133, 20)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);
            VerifyNotAnOutLocal(model, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);
            VerifyNotAnOutLocal(model, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").Single();
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").Single();
            VerifyModelForOutVarDuplicateInSameScope(model, x7Decl);
            VerifyNotAnOutLocal(model, x7Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(4, x8Decl.Length);
            Assert.Equal(4, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl[0], x8Ref[0], x8Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl[1]);
            VerifyModelForOutVar(model, x8Decl[2], x8Ref[2]);
            VerifyModelForOutVar(model, x8Decl[3], x8Ref[3]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(3, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[1], x9Ref[2]);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[2], x9Ref[3]);

            var x10Decl = GetOutVarDeclarations(tree, "x10").ToArray();
            var x10Ref = GetReferences(tree, "x10").ToArray();
            Assert.Equal(3, x10Decl.Length);
            Assert.Equal(4, x10Ref.Length);
            VerifyNotInScope(model, x10Ref[0]);
            VerifyModelForOutVar(model, x10Decl[0], x10Ref[1], x10Ref[2]);
            VerifyModelForOutVarDuplicateInSameScope(model, x10Decl[1]);
            VerifyModelForOutVar(model, x10Decl[2], x10Ref[3]);

            var x11Decl = GetOutVarDeclarations(tree, "x11").ToArray();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(3, x11Decl.Length);
            Assert.Equal(4, x11Ref.Length);
            VerifyNotInScope(model, x11Ref[0]);
            VerifyModelForOutVar(model, x11Decl[0], x11Ref[1], x11Ref[2]);
            VerifyModelForOutVarDuplicateInSameScope(model, x11Decl[1]);
            VerifyModelForOutVar(model, x11Decl[2], x11Ref[3]);

            var x12Decl = GetOutVarDeclarations(tree, "x12").ToArray();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(2, x12Decl.Length);
            Assert.Equal(4, x12Ref.Length);
            VerifyNotInScope(model, x12Ref[0]);
            VerifyModelForOutVar(model, x12Decl[0], x12Ref[1], x12Ref[2]);
            VerifyModelForOutVar(model, x12Decl[1], x12Ref[3]);

            var x13Decl = GetOutVarDeclarations(tree, "x13").ToArray();
            var x13Ref = GetReferences(tree, "x13").ToArray();
            Assert.Equal(2, x13Decl.Length);
            Assert.Equal(4, x13Ref.Length);
            VerifyNotInScope(model, x13Ref[0]);
            VerifyNotInScope(model, x13Ref[1]);
            VerifyModelForOutVar(model, x13Decl[0], x13Ref[2], x13Ref[3]);
            VerifyModelForOutVarDuplicateInSameScope(model, x13Decl[1]);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(4, x14Ref.Length);
            VerifyNotInScope(model, x14Ref[0]);
            VerifyNotInScope(model, x14Ref[1]);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref[2], x14Ref[3]);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

            var x15Decl = GetOutVarDeclarations(tree, "x15").Single();
            var x15Ref = GetReferences(tree, "x15").ToArray();
            Assert.Equal(4, x15Ref.Length);
            VerifyNotInScope(model, x15Ref[0]);
            VerifyNotInScope(model, x15Ref[1]);
            VerifyModelForOutVar(model, x15Decl, x15Ref[2], x15Ref[3]);
        }

        [Fact]
        public void Scope_For_07()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (;;
             Dummy(x1),
             Dummy(TakeOutParam(true, out var x1) && x1))
        {}
    }

    void Test2()
    {
        for (;;
             Dummy(TakeOutParam(true, out var x2) && x2),
             Dummy(TakeOutParam(true, out var x2) && x2))
        {}
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,20): error CS0841: Cannot use local variable 'x1' before it is declared
                //              Dummy(x1),
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(13, 20),
                // (22,47): error CS0128: A local variable or function named 'x2' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x2) && x2))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(22, 47)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl[1]);
        }

        [Fact]
        public void For_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        for (Dummy(f, TakeOutParam((f ? 10 : 20), out var x0), x0); 
             Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1); 
             Dummy(f, TakeOutParam((f ? 100 : 200), out var x2), x2), Dummy(true, null, x2))
        {
            System.Console.WriteLine(x0);
            System.Console.WriteLine(x1);
            f = false;
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"10
1
10
1
200
200
2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x0Decl = GetOutVarDeclarations(tree, "x0").Single();
            var x0Ref = GetReferences(tree, "x0").ToArray();
            Assert.Equal(2, x0Ref.Length);
            VerifyModelForOutVar(model, x0Decl, x0Ref);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);
        }

        [Fact]
        public void For_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        for (Dummy(f, TakeOutParam((f ? 10 : 20), out var x0), x0); 
             Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1); 
             f = false, Dummy(f, TakeOutParam((f ? 100 : 200), out var x2), x2), Dummy(true, null, x2))
        {
            System.Console.WriteLine(x0);
            System.Console.WriteLine(x1);
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"10
1
10
1
200
200
2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x0Decl = GetOutVarDeclarations(tree, "x0").Single();
            var x0Ref = GetReferences(tree, "x0").ToArray();
            Assert.Equal(2, x0Ref.Length);
            VerifyModelForOutVar(model, x0Decl, x0Ref);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);
        }

        [Fact]
        public void For_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        var l = new System.Collections.Generic.List<System.Action>();

        for (TakeOutParam(1, out var x0); Dummy(x0 < 3, TakeOutParam(x0*10, out var x1), x1); x0++)
        {
            l.Add(() => System.Console.WriteLine(""{0} {1}"", x0, x1));
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"10
20
30
--
3 10
3 20
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x0Decl = GetOutVarDeclarations(tree, "x0").ToArray();
            var x0Ref = GetReferences(tree, "x0").ToArray();
            Assert.Equal(1, x0Decl.Length);
            Assert.Equal(4, x0Ref.Length);
            VerifyModelForOutVar(model, x0Decl[0], x0Ref);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void For_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        var l = new System.Collections.Generic.List<System.Action>();

        for (TakeOutParam(1, out var x0); Dummy(x0 < 3, TakeOutParam(x0*10, out var x1), x1, l, () => System.Console.WriteLine(""{0} {1}"", x0, x1)); x0++)
        {
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static bool Dummy(bool x, object y, object z, System.Collections.Generic.List<System.Action> l, System.Action d) 
    {
        l.Add(d);
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"10
20
30
--
3 10
3 20
3 30
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x0Decl = GetOutVarDeclarations(tree, "x0").ToArray();
            var x0Ref = GetReferences(tree, "x0").ToArray();
            Assert.Equal(1, x0Decl.Length);
            Assert.Equal(4, x0Ref.Length);
            VerifyModelForOutVar(model, x0Decl[0], x0Ref);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void For_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        var l = new System.Collections.Generic.List<System.Action>();

        for (TakeOutParam(1, out var x0); Dummy(x0 < 3, TakeOutParam(x0*10, out var x1), x1, l, () => System.Console.WriteLine(""{0} {1}"", x0, x1)); x0++)
        {
            l.Add(() => System.Console.WriteLine(""{0} {1}"", x0, x1));
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static bool Dummy(bool x, object y, object z, System.Collections.Generic.List<System.Action> l, System.Action d) 
    {
        l.Add(d);
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"10
20
30
--
3 10
3 10
3 20
3 20
3 30
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x0Decl = GetOutVarDeclarations(tree, "x0").ToArray();
            var x0Ref = GetReferences(tree, "x0").ToArray();
            Assert.Equal(1, x0Decl.Length);
            Assert.Equal(5, x0Ref.Length);
            VerifyModelForOutVar(model, x0Decl[0], x0Ref);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void For_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        var l = new System.Collections.Generic.List<System.Action>();

        for (int x0 = 1; x0 < 3; Dummy(TakeOutParam(x0*10, out var x1), x1, l, () => System.Console.WriteLine(""{0}"", x1)))
        {
            x0++;
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static void Dummy(object y, object z, System.Collections.Generic.List<System.Action> l, System.Action d) 
    {
        l.Add(d);
        System.Console.WriteLine(z);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"20
30
--
20
30
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void For_07()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        var l = new System.Collections.Generic.List<System.Action>();

        for (int x0 = 1; x0 < 3; Dummy(TakeOutParam(x0*10, out var x1), x1, l, () => System.Console.WriteLine(""{0}"", x1)), x0++)
        {
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static void Dummy(object y, object z, System.Collections.Generic.List<System.Action> l, System.Action d) 
    {
        l.Add(d);
        System.Console.WriteLine(z);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"10
20
--
10
20
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Scope_Foreach_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.Collections.IEnumerable Dummy(params object[] x) {return null;}

    void Test1()
    {
        foreach (var i in Dummy(TakeOutParam(true, out var x1) && x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        foreach (var i in Dummy(TakeOutParam(true, out var x2) && x2))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        foreach (var i in Dummy(TakeOutParam(true, out var x4) && x4))
            Dummy(x4);
    }

    void Test6()
    {
        foreach (var i in Dummy(x6 && TakeOutParam(true, out var x6)))
            Dummy(x6);
    }

    void Test7()
    {
        foreach (var i in Dummy(TakeOutParam(true, out var x7) && x7))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        foreach (var i in Dummy(TakeOutParam(true, out var x8) && x8))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        foreach (var i1 in Dummy(TakeOutParam(true, out var x9) && x9))
        {   
            Dummy(x9);
            foreach (var i2 in Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        foreach (var i in Dummy(TakeOutParam(y10, out var x10)))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    foreach (var i in Dummy(TakeOutParam(y11, out var x11)))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        foreach (var i in Dummy(TakeOutParam(y12, out var x12)))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    foreach (var i in Dummy(TakeOutParam(y13, out var x13)))
    //        let y13 = 12;
    //}

    void Test14()
    {
        foreach (var i in Dummy(TakeOutParam(1, out var x14), 
                                TakeOutParam(2, out var x14), 
                                x14))
        {
            Dummy(x14);
        }
    }

    void Test15()
    {
        foreach (var x15 in 
                            Dummy(TakeOutParam(1, out var x15), x15))
        {
            Dummy(x15);
        }
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }

    static bool TakeOutParam(bool y, out bool x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,60): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         foreach (var i in Dummy(TakeOutParam(true, out var x4) && x4))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 60),
                // (35,33): error CS0841: Cannot use local variable 'x6' before it is declared
                //         foreach (var i in Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 33),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,65): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             foreach (var i2 in Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 65),
                // (68,46): error CS0103: The name 'y10' does not exist in the current context
                //         foreach (var i in Dummy(TakeOutParam(y10, out var x10)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 46),
                // (86,46): error CS0103: The name 'y12' does not exist in the current context
                //         foreach (var i in Dummy(TakeOutParam(y12, out var x12)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 46),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,57): error CS0128: A local variable named 'x14' is already defined in this scope
                //                                 TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 57),
                // (108,22): error CS0136: A local or parameter named 'x15' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         foreach (var x15 in 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x15").WithArguments("x15").WithLocation(108, 22)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

            var x15Decl = GetOutVarDeclarations(tree, "x15").Single();
            var x15Ref = GetReferences(tree, "x15").ToArray();
            Assert.Equal(2, x15Ref.Length);
            VerifyModelForOutVar(model, x15Decl, x15Ref[0]);
            VerifyNotAnOutLocal(model, x15Ref[1]);
        }

        [Fact]
        public void Foreach_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        foreach (var i in Dummy(TakeOutParam(3, out var x1), x1))
        {
            System.Console.WriteLine(x1);
        }
    }

    static System.Collections.IEnumerable Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return ""a"";
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"3
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Scope_If_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        if (TakeOutParam(true, out var x1))
        {
            Dummy(x1);
        }
        else
        {
            System.Console.WriteLine(x1);
        }
    }

    void Test2()
    {
        if (TakeOutParam(true, out var x2))
            Dummy(x2);
        else
            System.Console.WriteLine(x2);
    }

    void Test3()
    {
        if (TakeOutParam(true, out var x3))
            Dummy(x3);
        else
        {
            var x3 = 12;
            System.Console.WriteLine(x3);
        }
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        if (TakeOutParam(true, out var x4))
            Dummy(x4);
    }

    void Test5(int x5)
    {
        if (TakeOutParam(true, out var x5))
            Dummy(x5);
    }

    void Test6()
    {
        if (x6 && TakeOutParam(true, out var x6))
            Dummy(x6);
    }

    void Test7()
    {
        if (TakeOutParam(true, out var x7) && x7)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        if (TakeOutParam(true, out var x8))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        if (TakeOutParam(true, out var x9))
        {   
            Dummy(x9);
            if (TakeOutParam(true, out var x9)) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        if (TakeOutParam(y10, out var x10))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    void Test12()
    {
        if (TakeOutParam(y12, out var x12))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    if (TakeOutParam(y13, out var x13))
    //        let y13 = 12;
    //}

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }

    static bool TakeOutParam(bool y, out bool x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (101,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(101, 13),
                // (36,17): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x3 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(36, 17),
                // (46,40): error CS0128: A local variable named 'x4' is already defined in this scope
                //         if (TakeOutParam(true, out var x4))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(46, 40),
                // (52,40): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         if (TakeOutParam(true, out var x5))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(52, 40),
                // (58,13): error CS0841: Cannot use local variable 'x6' before it is declared
                //         if (x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(58, 13),
                // (66,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(66, 17),
                // (83,19): error CS0841: Cannot use local variable 'x9' before it is declared
                //             Dummy(x9);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x9").WithArguments("x9").WithLocation(83, 19),
                // (84,44): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             if (TakeOutParam(true, out var x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(84, 44),
                // (91,26): error CS0103: The name 'y10' does not exist in the current context
                //         if (TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(91, 26),
                // (100,26): error CS0103: The name 'y12' does not exist in the current context
                //         if (TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(100, 26),
                // (101,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(101, 17)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            VerifyModelForOutVar(model, x3Decl, x3Ref[0]);
            VerifyNotAnOutLocal(model, x3Ref[1]);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").Single();
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(2, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);
        }

        [Fact]
        public void Scope_If_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        if (true)
            if (TakeOutParam(true, out var x1))
            {
            }
            else
            {
            }

        x1++;
    }

    static bool TakeOutParam(bool y, out bool x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (20,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(20, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl);
            VerifyNotInScope(model, x1Ref);
        }

        [Fact]
        public void Scope_If_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (IfStatementSyntax)SyntaxFactory.ParseStatement(@"
if (Dummy(TakeOutParam(true, out var x1), x1));
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void If_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
        Test(2);
    }

    public static void Test(int val)
    {
        if (Dummy(val == 1, TakeOutParam(val, out var x1), x1))
        {
            System.Console.WriteLine(""true"");
            System.Console.WriteLine(x1);
        }
        else
        {
            System.Console.WriteLine(""false"");
            System.Console.WriteLine(x1);
        }

        System.Console.WriteLine(x1);
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
true
1
1
2
false
2
2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(4, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void If_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        if (f)        
            if (Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1))
                ;

        if (f)        
        {
            if (Dummy(f, TakeOutParam((f ? 3 : 4), out var x1), x1))
                ;
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void Scope_Lambda_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    System.Action<object> Test1()
    {
        return (o) => let x1 = o;
    }

    System.Action<object> Test2()
    {
        return (o) => let var x2 = o;
    }

    void Test3()
    {
        Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x3) && x3 > 0));
    }

    void Test4()
    {
        Dummy((System.Func<object, bool>) (o => x4 && TakeOutParam(o, out int x4)));
    }

    void Test5()
    {
        Dummy((System.Func<object, object, bool>) ((o1, o2) => TakeOutParam(o1, out int x5) && 
                                                               TakeOutParam(o2, out int x5) && 
                                                               x5 > 0));
    }

    void Test6()
    {
        Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x6) && x6 > 0), (System.Func<object, bool>) (o => TakeOutParam(o, out int x6) && x6 > 0));
    }

    void Test7()
    {
        Dummy(x7, 1);
        Dummy(x7, 
             (System.Func<object, bool>) (o => TakeOutParam(o, out int x7) && x7 > 0), 
              x7);
        Dummy(x7, 2); 
    }

    void Test8()
    {
        Dummy(TakeOutParam(true, out var x8) && x8, (System.Func<object, bool>) (o => TakeOutParam(o, out int y8) && x8));
    }

    void Test9()
    {
        Dummy(TakeOutParam(true, out var x9), 
              (System.Func<object, bool>) (o => TakeOutParam(o, out int x9) && 
                                                x9 > 0), x9);
    }

    void Test10()
    {
        Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x10) && 
                                                x10 > 0),
              TakeOutParam(true, out var x10), x10);
    }

    void Test11()
    {
        var x11 = 11;
        Dummy(x11);
        Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x11) && 
                                                x11 > 0), x11);
    }

    void Test12()
    {
        Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x12) && 
                                                x12 > 0), 
              x12);
        var x12 = 11;
        Dummy(x12);
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }

    static bool TakeOutParam(bool y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (12,27): error CS1002: ; expected
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_SemicolonExpected, "x1").WithLocation(12, 27),
                // (17,27): error CS1002: ; expected
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_SemicolonExpected, "var").WithLocation(17, 27),
                // (12,23): error CS0103: The name 'let' does not exist in the current context
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "let").WithArguments("let").WithLocation(12, 23),
                // (12,23): error CS0201: Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_IllegalStatement, "let").WithLocation(12, 23),
                // (12,27): error CS0103: The name 'x1' does not exist in the current context
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(12, 27),
                // (12,32): error CS0103: The name 'o' does not exist in the current context
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "o").WithArguments("o").WithLocation(12, 32),
                // (12,27): warning CS0162: Unreachable code detected
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.WRN_UnreachableCode, "x1").WithLocation(12, 27),
                // (17,23): error CS0103: The name 'let' does not exist in the current context
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "let").WithArguments("let").WithLocation(17, 23),
                // (17,23): error CS0201: Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_IllegalStatement, "let").WithLocation(17, 23),
                // (17,36): error CS0103: The name 'o' does not exist in the current context
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "o").WithArguments("o").WithLocation(17, 36),
                // (17,27): warning CS0162: Unreachable code detected
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.WRN_UnreachableCode, "var").WithLocation(17, 27),
                // (27,49): error CS0841: Cannot use local variable 'x4' before it is declared
                //         Dummy((System.Func<object, bool>) (o => x4 && TakeOutParam(o, out int x4)));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(27, 49),
                // (33,89): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                                                                TakeOutParam(o2, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(33, 89),
                // (44,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(44, 15),
                // (45,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(45, 15),
                // (47,15): error CS0103: The name 'x7' does not exist in the current context
                //               x7);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(47, 15),
                // (48,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(48, 15),
                // (82,15): error CS0841: Cannot use local variable 'x12' before it is declared
                //               x12);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x12").WithArguments("x12").WithLocation(82, 15)
                );

            compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_3);
            compilation.VerifyDiagnostics(
                // (12,27): error CS1002: ; expected
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_SemicolonExpected, "x1").WithLocation(12, 27),
                // (17,27): error CS1002: ; expected
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_SemicolonExpected, "var").WithLocation(17, 27),
                // (12,23): error CS0103: The name 'let' does not exist in the current context
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "let").WithArguments("let").WithLocation(12, 23),
                // (12,23): error CS0201: Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_IllegalStatement, "let").WithLocation(12, 23),
                // (12,27): error CS0103: The name 'x1' does not exist in the current context
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(12, 27),
                // (12,32): error CS0103: The name 'o' does not exist in the current context
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "o").WithArguments("o").WithLocation(12, 32),
                // (12,27): warning CS0162: Unreachable code detected
                //         return (o) => let x1 = o;
                Diagnostic(ErrorCode.WRN_UnreachableCode, "x1").WithLocation(12, 27),
                // (17,23): error CS0103: The name 'let' does not exist in the current context
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "let").WithArguments("let").WithLocation(17, 23),
                // (17,23): error CS0201: Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_IllegalStatement, "let").WithLocation(17, 23),
                // (17,36): error CS0103: The name 'o' does not exist in the current context
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "o").WithArguments("o").WithLocation(17, 36),
                // (17,27): warning CS0162: Unreachable code detected
                //         return (o) => let var x2 = o;
                Diagnostic(ErrorCode.WRN_UnreachableCode, "var").WithLocation(17, 27),
                // (27,49): error CS0841: Cannot use local variable 'x4' before it is declared
                //         Dummy((System.Func<object, bool>) (o => x4 && TakeOutParam(o, out int x4)));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(27, 49),
                // (33,89): error CS0128: A local variable named 'x5' is already defined in this scope
                //                                                                TakeOutParam(o2, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(33, 89),
                // (44,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(44, 15),
                // (45,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(45, 15),
                // (47,15): error CS0103: The name 'x7' does not exist in the current context
                //               x7);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(47, 15),
                // (48,15): error CS0103: The name 'x7' does not exist in the current context
                //         Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(48, 15),
                // (59,73): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //               (System.Func<object, bool>) (o => TakeOutParam(o, out int x9) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(59, 73),
                // (65,73): error CS0136: A local or parameter named 'x10' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x10) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x10").WithArguments("x10").WithLocation(65, 73),
                // (74,73): error CS0136: A local or parameter named 'x11' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x11) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x11").WithArguments("x11").WithLocation(74, 73),
                // (80,73): error CS0136: A local or parameter named 'x12' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out int x12) && 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x12").WithArguments("x12").WithLocation(80, 73),
                // (82,15): error CS0841: Cannot use local variable 'x12' before it is declared
                //               x12);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x12").WithArguments("x12").WithLocation(82, 15)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(5, x7Ref.Length);
            VerifyNotInScope(model, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyModelForOutVar(model, x7Decl, x7Ref[2]);
            VerifyNotInScope(model, x7Ref[3]);
            VerifyNotInScope(model, x7Ref[4]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(2, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[0]);

            var x10Decl = GetOutVarDeclarations(tree, "x10").ToArray();
            var x10Ref = GetReferences(tree, "x10").ToArray();
            Assert.Equal(2, x10Decl.Length);
            Assert.Equal(2, x10Ref.Length);
            VerifyModelForOutVar(model, x10Decl[0], x10Ref[0]);
            VerifyModelForOutVar(model, x10Decl[1], x10Ref[1]);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(3, x11Ref.Length);
            VerifyNotAnOutLocal(model, x11Ref[0]);
            VerifyModelForOutVar(model, x11Decl, x11Ref[1]);
            VerifyNotAnOutLocal(model, x11Ref[2]);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(3, x12Ref.Length);
            VerifyModelForOutVar(model, x12Decl, x12Ref[0]);
            VerifyNotAnOutLocal(model, x12Ref[1]);
            VerifyNotAnOutLocal(model, x12Ref[2]);
        }

        [Fact]
        public void Lambda_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static bool Test1()
    {
        System.Func<bool> l = () => TakeOutParam(1, out int x1) && Dummy(x1); 
        return l();
    }

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Scope_LocalDeclarationStmt_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        var d = Dummy(TakeOutParam(true, out var x1), x1);
    }
    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        var d = Dummy(TakeOutParam(true, out var x4), x4);
    }

    void Test6()
    {
        var d = Dummy(x6 && TakeOutParam(true, out var x6));
    }

    void Test8()
    {
        var d = Dummy(TakeOutParam(true, out var x8), x8);
        System.Console.WriteLine(x8);
    }

    void Test14()
    {
        var d = Dummy(TakeOutParam(1, out var x14), 
                      TakeOutParam(2, out var x14), 
                      x14);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (19,50): error CS0128: A local variable named 'x4' is already defined in this scope
                //         var d = Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(19, 50),
                // (24,23): error CS0841: Cannot use local variable 'x6' before it is declared
                //         var d = Dummy(x6 && TakeOutParam(true, out var x6));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(24, 23),
                // (36,47): error CS0128: A local variable named 'x14' is already defined in this scope
                //                       TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(36, 47)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").Single();
            Assert.Equal(2, x14Decl.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_LocalDeclarationStmt_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        object d = Dummy(TakeOutParam(true, out var x1), x1);
    }
    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        object d = Dummy(TakeOutParam(true, out var x4), x4);
    }

    void Test6()
    {
        object d = Dummy(x6 && TakeOutParam(true, out var x6));
    }

    void Test8()
    {
        object d = Dummy(TakeOutParam(true, out var x8), x8);
        System.Console.WriteLine(x8);
    }

    void Test14()
    {
        object d = Dummy(TakeOutParam(1, out var x14), 
                         TakeOutParam(2, out var x14), 
                         x14);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (19,53): error CS0128: A local variable named 'x4' is already defined in this scope
                //         object d = Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(19, 53),
                // (24,26): error CS0841: Cannot use local variable 'x6' before it is declared
                //         object d = Dummy(x6 && TakeOutParam(true, out var x6));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(24, 26),
                // (36,50): error CS0128: A local variable named 'x14' is already defined in this scope
                //                          TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(36, 50)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").Single();
            Assert.Equal(2, x14Decl.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_LocalDeclarationStmt_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        var x1 = 
                 Dummy(TakeOutParam(true, out var x1), x1);
        Dummy(x1);
    }

    void Test2()
    {
        object x2 = 
                    Dummy(TakeOutParam(true, out var x2), x2);
        Dummy(x2);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,51): error CS0128: A local variable named 'x1' is already defined in this scope
                //                  Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 51),
                // (13,56): error CS0841: Cannot use local variable 'x1' before it is declared
                //                  Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(13, 56),
                // (20,54): error CS0128: A local variable named 'x2' is already defined in this scope
                //                     Dummy(TakeOutParam(true, out var x2), x2);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 54),
                // (20,59): error CS0165: Use of unassigned local variable 'x2'
                //                     Dummy(TakeOutParam(true, out var x2), x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(20, 59)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyNotAnOutLocal(model, x2Ref[0]);
            VerifyNotAnOutLocal(model, x2Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
        }

        [Fact]
        public void Scope_LocalDeclarationStmt_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

   object Dummy(params object[] x) {return null;}

    void Test1()
    {
        object d = Dummy(TakeOutParam(true, out var x1), x1), 
               x1 = Dummy(x1);
        Dummy(x1);
    }

    void Test2()
    {
        object d1 = Dummy(TakeOutParam(true, out var x2), x2), 
               d2 = Dummy(TakeOutParam(true, out var x2), x2);
    }

    void Test3()
    {
        object d1 = Dummy(TakeOutParam(true, out var x3), x3), 
               d2 = Dummy(x3);
    }

    void Test4()
    {
        object d1 = Dummy(x4), 
               d2 = Dummy(TakeOutParam(true, out var x4), x4);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,16): error CS0128: A local variable named 'x1' is already defined in this scope
                //                x1 = Dummy(x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 16),
                // (20,54): error CS0128: A local variable named 'x2' is already defined in this scope
                //                d2 = Dummy(TakeOutParam(true, out var x2), x2);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 54),
                // (31,27): error CS0841: Cannot use local variable 'x4' before it is declared
                //         object d1 = Dummy(x4), 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(31, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl[1]);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyModelForOutVar(model, x4Decl, x4Ref);
        }

        [Fact]
        public void Scope_LocalDeclarationStmt_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    long Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (LocalDeclarationStatementSyntax)SyntaxFactory.ParseStatement(@"
var y1 = Dummy(TakeOutParam(true, out var x1), x1);
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());

            Assert.Equal("System.Int64 y1", model.LookupSymbols(x1Ref[0].SpanStart, name: "y1").Single().ToTestDisplayString());
        }

        [Fact]
        public void Scope_LocalDeclarationStmt_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Test1()
    {
        if (true)
            var d =TakeOutParam(true, out var x1) && x1 != null;

        x1++;
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (11,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var d =TakeOutParam(true, out var x1) && x1 != null;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var d =TakeOutParam(true, out var x1) && x1 != null;").WithLocation(11, 13),
                // (13,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(13, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref[0]);
            VerifyNotInScope(model, x1Ref[1]);

            var d = tree.GetRoot().DescendantNodes().OfType<VariableDeclaratorSyntax>().Where(id => id.Identifier.ValueText == "d").Single();
            Assert.Equal("System.Boolean d", model.GetDeclaredSymbol(d).ToTestDisplayString());
        }

        [Fact]
        public void LocalDeclarationStmt_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        object d1 = Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1), x1),
               d2 = Dummy(new C(""c""), TakeOutParam(new C(""d""), out var x2), x2);
        System.Console.WriteLine(d1);
        System.Console.WriteLine(d2);
        System.Console.WriteLine(x1);
    }

    static object Dummy(object x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}

class C
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"b
d
a
c
b");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void LocalDeclarationStmt_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        if (true)
        {
            object d1 = Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1), x1);
        }
    }

    static object Dummy(object x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}

class C
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"b");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_DeconstructionDeclarationStmt_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        var (d, dd) = (TakeOutParam(true, out var x1), x1);
    }
    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        var (d, dd) = (TakeOutParam(true, out var x4), x4);
    }

    void Test6()
    {
        var (d, dd) = (x6 && TakeOutParam(true, out var x6), 1);
    }

    void Test8()
    {
        var (d, dd) = (TakeOutParam(true, out var x8), x8);
        System.Console.WriteLine(x8);
    }

    void Test14()
    {
        var (d, dd, ddd) = (TakeOutParam(1, out var x14), 
                      TakeOutParam(2, out var x14), 
                      x14);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (19,51): error CS0128: A local variable named 'x4' is already defined in this scope
                //         var (d, dd) = (TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(19, 51),
                // (24,24): error CS0841: Cannot use local variable 'x6' before it is declared
                //         var (d, dd) = (x6 && TakeOutParam(true, out var x6), 1);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(24, 24),
                // (36,47): error CS0128: A local variable named 'x14' is already defined in this scope
                //                       TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(36, 47)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").Single();
            Assert.Equal(2, x14Decl.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_DeconstructionDeclarationStmt_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        (object d, object dd) = (TakeOutParam(true, out var x1), x1);
    }
    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        (object d, object dd) = (TakeOutParam(true, out var x4), x4);
    }

    void Test6()
    {
        (object d, object dd) = (x6 && TakeOutParam(true, out var x6), 1);
    }

    void Test8()
    {
        (object d, object dd) = (TakeOutParam(true, out var x8), x8);
        System.Console.WriteLine(x8);
    }

    void Test14()
    {
        (object d, object dd, object ddd) = (TakeOutParam(1, out var x14), 
                      TakeOutParam(2, out var x14), 
                      x14);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (19,61): error CS0128: A local variable named 'x4' is already defined in this scope
                //         (object d, object dd) = (TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(19, 61),
                // (24,34): error CS0841: Cannot use local variable 'x6' before it is declared
                //         (object d, object dd) = (x6 && TakeOutParam(true, out var x6), 1);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(24, 34),
                // (36,47): error CS0128: A local variable named 'x14' is already defined in this scope
                //                       TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(36, 47)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").Single();
            Assert.Equal(2, x14Decl.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_DeconstructionDeclarationStmt_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        var (x1, dd) = 
                      (TakeOutParam(true, out var x1), x1);
        Dummy(x1);
    }

    void Test2()
    {
        (object x2, object dd) = 
                         (TakeOutParam(true, out var x2), x2);
        Dummy(x2);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,51): error CS0128: A local variable named 'x1' is already defined in this scope
                //                       (TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 51),
                // (13,56): error CS0841: Cannot use local variable 'x1' before it is declared
                //                       (TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(13, 56),
                // (20,54): error CS0128: A local variable named 'x2' is already defined in this scope
                //                          (TakeOutParam(true, out var x2), x2);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 54),
                // (20,59): error CS0165: Use of unassigned local variable 'x2'
                //                          (TakeOutParam(true, out var x2), x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(20, 59)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyNotAnOutLocal(model, x2Ref[0]);
            VerifyNotAnOutLocal(model, x2Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_DeconstructionDeclarationStmt_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        (object d, object x1) = (Dummy(TakeOutParam(true, out var x1), x1), 
                                Dummy(x1));
        Dummy(x1);
    }

    void Test2()
    {
        (object d1, object d2) = (Dummy(TakeOutParam(true, out var x2), x2), 
                    Dummy(TakeOutParam(true, out var x2), x2));
    }

    void Test3()
    {
        (object d1, object d2) = (Dummy(TakeOutParam(true, out var x3), x3), 
                    Dummy(x3));
    }

    void Test4()
    {
        (object d1, object d2) = (Dummy(x4), 
                    Dummy(TakeOutParam(true, out var x4), x4));
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (12,67): error CS0128: A local variable named 'x1' is already defined in this scope
                //         (object d, object x1) = (Dummy(TakeOutParam(true, out var x1), x1), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(12, 67),
                // (12,72): error CS0165: Use of unassigned local variable 'x1'
                //         (object d, object x1) = (Dummy(TakeOutParam(true, out var x1), x1), 
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(12, 72),
                // (20,54): error CS0128: A local variable named 'x2' is already defined in this scope
                //                     Dummy(TakeOutParam(true, out var x2), x2));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 54),
                // (31,41): error CS0841: Cannot use local variable 'x4' before it is declared
                //         (object d1, object d2) = (Dummy(x4), 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(31, 41)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);
            VerifyNotAnOutLocal(model, x1Ref[2]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl[1]);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyModelForOutVar(model, x4Decl, x4Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_DeconstructionDeclarationStmt_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (ExpressionStatementSyntax)SyntaxFactory.ParseStatement(@"
var (y1, dd) = (TakeOutParam(true, out var x1), x1);
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());

            Assert.Equal("System.Boolean y1", model.LookupSymbols(x1Ref[0].SpanStart, name: "y1").Single().ToTestDisplayString());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_DeconstructionDeclarationStmt_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Test1()
    {
        if (true)
            var (d, dd) = (TakeOutParam(true, out var x1), x1);

        x1++;
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(13, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref[0]);
            VerifyNotInScope(model, x1Ref[1]);

            var d = tree.GetRoot().DescendantNodes().OfType<SingleVariableDesignationSyntax>().Where(id => id.Identifier.ValueText == "d").Single();
            Assert.Equal("System.Boolean d", model.GetDeclaredSymbol(d).ToTestDisplayString());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void DeconstructionDeclarationStmt_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        (object d1, object d2) = (Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1), x1),
                                 Dummy(new C(""c""), TakeOutParam(new C(""d""), out var x2), x2));
        System.Console.WriteLine(d1);
        System.Console.WriteLine(d2);
        System.Console.WriteLine(x1);
    }

    static object Dummy(object x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}

class C
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"b
d
a
c
b");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void DeconstructionDeclarationStmt_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        if (true)
        {
            (object d1, object d2) = (Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1), x1), x1);
        }
    }

    static object Dummy(object x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}

class C
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"b");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void DeconstructionDeclarationStmt_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        var (d1, (d2, d3)) = (Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1), x1),
                              (Dummy(new C(""c""), TakeOutParam(new C(""d""), out var x2), x2),
                               Dummy(new C(""e""), TakeOutParam(new C(""f""), out var x3), x3)));
        System.Console.WriteLine(d1);
        System.Console.WriteLine(d2);
        System.Console.WriteLine(d3);
        System.Console.WriteLine(x1);
        System.Console.WriteLine(x2);
        System.Console.WriteLine(x3);
    }

    static object Dummy(object x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}

class C
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"b
d
f
a
c
e
b
d
f");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(1, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").ToArray();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(1, x3Decl.Length);
            Assert.Equal(2, x3Ref.Length);
            VerifyModelForOutVar(model, x3Decl[0], x3Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void DeconstructionDeclarationStmt_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        (var d1, (var d2, var d3)) = (Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1), x1),
                              (Dummy(new C(""c""), TakeOutParam(new C(""d""), out var x2), x2),
                               Dummy(new C(""e""), TakeOutParam(new C(""f""), out var x3), x3)));
        System.Console.WriteLine(d1);
        System.Console.WriteLine(d2);
        System.Console.WriteLine(d3);
        System.Console.WriteLine(x1);
        System.Console.WriteLine(x2);
        System.Console.WriteLine(x3);
    }

    static object Dummy(object x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}

class C
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"b
d
f
a
c
e
b
d
f");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(1, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").ToArray();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(1, x3Decl.Length);
            Assert.Equal(2, x3Ref.Length);
            VerifyModelForOutVar(model, x3Decl[0], x3Ref);
        }

        [Fact]
        public void Scope_Lock_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        lock (Dummy(TakeOutParam(true, out var x1) && x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        lock (Dummy(TakeOutParam(true, out var x2) && x2))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        lock (Dummy(TakeOutParam(true, out var x4) && x4 > 0))
            Dummy(x4);
    }

    void Test6()
    {
        lock (Dummy(x6 && TakeOutParam(true, out var x6)))
            Dummy(x6);
    }

    void Test7()
    {
        lock (Dummy(TakeOutParam(true, out var x7) && x7))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        lock (Dummy(TakeOutParam(true, out var x8) && x8))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        lock (Dummy(TakeOutParam(true, out var x9) && x9))
        {   
            Dummy(x9);
            lock (Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        lock (Dummy(TakeOutParam(y10, out var x10)))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    lock (Dummy(TakeOutParam(y11, out var x11)))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        lock (Dummy(TakeOutParam(y12, out var x12)))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    lock (Dummy(TakeOutParam(y13, out var x13)))
    //        let y13 = 12;
    //}

    void Test14()
    {
        lock (Dummy(TakeOutParam(1, out var x14), 
                    TakeOutParam(2, out var x14), 
                    x14))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(bool y, out bool x) 
    {
        x = y;
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,48): error CS0128: A local variable named 'x4' is already defined in this scope
                //         lock (Dummy(TakeOutParam(true, out var x4) && x4 > 0))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(29, 48),
                // (35,21): error CS0841: Cannot use local variable 'x6' before it is declared
                //         lock (Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 21),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (60,19): error CS0841: Cannot use local variable 'x9' before it is declared
                //             Dummy(x9);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x9").WithArguments("x9").WithLocation(60, 19),
                // (61,52): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             lock (Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 52),
                // (68,34): error CS0103: The name 'y10' does not exist in the current context
                //         lock (Dummy(TakeOutParam(y10, out var x10)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 34),
                // (86,34): error CS0103: The name 'y12' does not exist in the current context
                //         lock (Dummy(TakeOutParam(y12, out var x12)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 34),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,45): error CS0128: A local variable named 'x14' is already defined in this scope
                //                     TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 45)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyNotAnOutLocal(model, x4Ref[2]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_Lock_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        if (true)
            lock (Dummy(TakeOutParam(true, out var x1)))
            {
            }

        x1++;
    }

    static object TakeOutParam(bool y, out bool x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (17,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(17, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl);
            VerifyNotInScope(model, x1Ref);
        }

        [Fact]
        public void Scope_Lock_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (LockStatementSyntax)SyntaxFactory.ParseStatement(@"
lock (Dummy(TakeOutParam(true, out var x1), x1)) ;
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Lock_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        lock (Dummy(TakeOutParam(""lock"", out var x1), x1))
        {
            System.Console.WriteLine(x1);
        }

        System.Console.WriteLine(x1);
    }

    static object Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new object();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"lock
lock
lock");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Lock_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        if (f)        
            lock (Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1))
                {}

        if (f)        
        {
            lock (Dummy(f, TakeOutParam((f ? 3 : 4), out var x1), x1))
                {}
        }
    }

    static object Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void Scope_ParameterDefault_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Test3(bool p = TakeOutParam(3, out int x3) && x3 > 0)
    {}

    void Test4(bool p = x4 && TakeOutParam(4, out int x4))
    {}

    void Test5(bool p = TakeOutParam(51, out int x5) && 
                        TakeOutParam(52, out int x5) && 
                        x5 > 0)
    {}

    void Test61(bool p1 = TakeOutParam(6, out int x6) && x6 > 0, bool p2 = TakeOutParam(6, out int x6) && x6 > 0)
    {}

    void Test71(bool p = TakeOutParam(7, out int x7) && x7 > 0)
    {
    }

    void Test72(bool p = x7 > 2)
    {}

    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,25): error CS1736: Default parameter value for 'p' must be a compile-time constant
                //     void Test3(bool p = TakeOutParam(3, out int x3) && x3 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(3, out int x3) && x3 > 0").WithArguments("p").WithLocation(8, 25),
                // (11,25): error CS0841: Cannot use local variable 'x4' before it is declared
                //     void Test4(bool p = x4 && TakeOutParam(4, out int x4))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(11, 25),
                // (15,50): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                         TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(15, 50),
                // (14,25): error CS1736: Default parameter value for 'p' must be a compile-time constant
                //     void Test5(bool p = TakeOutParam(51, out int x5) && 
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, @"TakeOutParam(51, out int x5) && 
                        TakeOutParam(52, out int x5) && 
                        x5 > 0").WithArguments("p").WithLocation(14, 25),
                // (19,27): error CS1736: Default parameter value for 'p1' must be a compile-time constant
                //     void Test61(bool p1 = TakeOutParam(6, out int x6) && x6 > 0, bool p2 = TakeOutParam(6, out int x6) && x6 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(6, out int x6) && x6 > 0").WithArguments("p1").WithLocation(19, 27),
                // (19,76): error CS1736: Default parameter value for 'p2' must be a compile-time constant
                //     void Test61(bool p1 = TakeOutParam(6, out int x6) && x6 > 0, bool p2 = TakeOutParam(6, out int x6) && x6 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(6, out int x6) && x6 > 0").WithArguments("p2").WithLocation(19, 76),
                // (22,26): error CS1736: Default parameter value for 'p' must be a compile-time constant
                //     void Test71(bool p = TakeOutParam(7, out int x7) && x7 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(7, out int x7) && x7 > 0").WithArguments("p").WithLocation(22, 26),
                // (26,26): error CS0103: The name 'x7' does not exist in the current context
                //     void Test72(bool p = x7 > 2)
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(26, 26),
                // (29,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(29, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);

            var node = tree.GetRoot().DescendantNodes().OfType<EqualsValueClauseSyntax>().First();

            compilation.VerifyOperationTree(node, expectedOperationTree:
@"
IParameterInitializerOperation (Parameter: [System.Boolean p = default(System.Boolean)]) (OperationKind.ParameterInitializer, Type: null, IsInvalid) (Syntax: '= TakeOutPa ... ) && x3 > 0')
  Locals: Local_1: System.Int32 x3
  IBinaryOperation (BinaryOperatorKind.ConditionalAnd) (OperationKind.Binary, Type: System.Boolean, IsInvalid) (Syntax: 'TakeOutPara ... ) && x3 > 0')
    Left: 
      IInvocationOperation (System.Boolean X.TakeOutParam(System.Int32 y, out System.Int32 x)) (OperationKind.Invocation, Type: System.Boolean, IsInvalid) (Syntax: 'TakeOutPara ... out int x3)')
        Instance Receiver: 
          null
        Arguments(2):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: y) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: '3')
              ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 3, IsInvalid) (Syntax: '3')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out int x3')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'int x3')
                ILocalReferenceOperation: x3 (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x3')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
    Right: 
      IBinaryOperation (BinaryOperatorKind.GreaterThan) (OperationKind.Binary, Type: System.Boolean, IsInvalid) (Syntax: 'x3 > 0')
        Left: 
          ILocalReferenceOperation: x3 (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x3')
        Right: 
          ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 0, IsInvalid) (Syntax: '0')
");
        }

        [Fact]
        public void Scope_ParameterDefault_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Test3(bool p = TakeOutParam(3, out var x3) && x3 > 0)
    {}

    void Test4(bool p = x4 && TakeOutParam(4, out var x4))
    {}

    void Test5(bool p = TakeOutParam(51, out var x5) && 
                        TakeOutParam(52, out var x5) && 
                        x5 > 0)
    {}

    void Test61(bool p1 = TakeOutParam(6, out var x6) && x6 > 0, bool p2 = TakeOutParam(6, out var x6) && x6 > 0)
    {}

    void Test71(bool p = TakeOutParam(7, out var x7) && x7 > 0)
    {
    }

    void Test72(bool p = x7 > 2)
    {}

    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,25): error CS1736: Default parameter value for 'p' must be a compile-time constant
                //     void Test3(bool p = TakeOutParam(3, out var x3) && x3 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(3, out var x3) && x3 > 0").WithArguments("p").WithLocation(8, 25),
                // (11,25): error CS0841: Cannot use local variable 'x4' before it is declared
                //     void Test4(bool p = x4 && TakeOutParam(4, out var x4))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(11, 25),
                // (15,50): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                         TakeOutParam(52, out var x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(15, 50),
                // (14,25): error CS1736: Default parameter value for 'p' must be a compile-time constant
                //     void Test5(bool p = TakeOutParam(51, out var x5) && 
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, @"TakeOutParam(51, out var x5) && 
                        TakeOutParam(52, out var x5) && 
                        x5 > 0").WithArguments("p").WithLocation(14, 25),
                // (19,27): error CS1736: Default parameter value for 'p1' must be a compile-time constant
                //     void Test61(bool p1 = TakeOutParam(6, out var x6) && x6 > 0, bool p2 = TakeOutParam(6, out var x6) && x6 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(6, out var x6) && x6 > 0").WithArguments("p1").WithLocation(19, 27),
                // (19,76): error CS1736: Default parameter value for 'p2' must be a compile-time constant
                //     void Test61(bool p1 = TakeOutParam(6, out var x6) && x6 > 0, bool p2 = TakeOutParam(6, out var x6) && x6 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(6, out var x6) && x6 > 0").WithArguments("p2").WithLocation(19, 76),
                // (22,26): error CS1736: Default parameter value for 'p' must be a compile-time constant
                //     void Test71(bool p = TakeOutParam(7, out var x7) && x7 > 0)
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "TakeOutParam(7, out var x7) && x7 > 0").WithArguments("p").WithLocation(22, 26),
                // (26,26): error CS0103: The name 'x7' does not exist in the current context
                //     void Test72(bool p = x7 > 2)
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(26, 26),
                // (29,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(29, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_PropertyInitializers_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Test3 {get;} = TakeOutParam(3, out int x3) && x3 > 0;

    bool Test4 {get;} = x4 && TakeOutParam(4, out int x4);

    bool Test5 {get;} = TakeOutParam(51, out int x5) && 
                 TakeOutParam(52, out int x5) && 
                 x5 > 0;

    bool Test61 {get;} = TakeOutParam(6, out int x6) && x6 > 0; bool Test62 {get;} = TakeOutParam(6, out int x6) && x6 > 0;

    bool Test71 {get;} = TakeOutParam(7, out int x7) && x7 > 0; 
    bool Test72 {get;} = Dummy(x7, 2); 
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (10,25): error CS0841: Cannot use local variable 'x4' before it is declared
                //     bool Test4 {get;} = x4 && TakeOutParam(4, out int x4);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(10, 25),
                // (13,43): error CS0128: A local variable named 'x5' is already defined in this scope
                //                  TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(13, 43),
                // (19,32): error CS0103: The name 'x7' does not exist in the current context
                //     bool Test72 {get;} = Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(19, 32),
                // (20,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(20, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            VerifyModelForOutVar(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVar(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
            VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void PropertyInitializers_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1);
    }

    static bool Test1 {get;} = TakeOutParam(1, out int x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");

            CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_2).VerifyDiagnostics(
                // (9,52): error CS8320: Feature 'declaration of expression variables in member initializers and queries' is not available in C# 7.2. Please use language version 7.3 or greater.
                //     static bool Test1 {get;} = TakeOutParam(1, out int x1) && Dummy(x1); 
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion7_2, "int x1").WithArguments("declaration of expression variables in member initializers and queries", "7.3").WithLocation(9, 52)
                );
            var tree = compilation.SyntaxTrees.Single();
            var node = tree.GetRoot().DescendantNodes().OfType<EqualsValueClauseSyntax>().Single();

            compilation.VerifyOperationTree(node, expectedOperationTree:
@"
IPropertyInitializerOperation (Property: System.Boolean X.Test1 { get; }) (OperationKind.PropertyInitializer, Type: null) (Syntax: '= TakeOutPa ... & Dummy(x1)')
  Locals: Local_1: System.Int32 x1
  IBinaryOperation (BinaryOperatorKind.ConditionalAnd) (OperationKind.Binary, Type: System.Boolean) (Syntax: 'TakeOutPara ... & Dummy(x1)')
    Left: 
      IInvocationOperation (System.Boolean X.TakeOutParam(System.Int32 y, out System.Int32 x)) (OperationKind.Invocation, Type: System.Boolean) (Syntax: 'TakeOutPara ... out int x1)')
        Instance Receiver: 
          null
        Arguments(2):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: y) (OperationKind.Argument, Type: null) (Syntax: '1')
              ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 1) (Syntax: '1')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null) (Syntax: 'out int x1')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32) (Syntax: 'int x1')
                ILocalReferenceOperation: x1 (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x1')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
    Right: 
      IInvocationOperation (System.Boolean X.Dummy(System.Int32 x)) (OperationKind.Invocation, Type: System.Boolean) (Syntax: 'Dummy(x1)')
        Instance Receiver: 
          null
        Arguments(1):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null) (Syntax: 'x1')
              ILocalReferenceOperation: x1 (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x1')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
        }

        [Fact]
        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
        public void PropertyInitializers_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static System.Func<bool> Test1 {get;} = () => TakeOutParam(1, out int x1) && Dummy(x1); 

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");
        }

        [Fact]
        public void PropertyInitializers_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }
    static bool a = false;
    bool Test1 { get; } = a && TakeOutParam(3, out int x1) || x1 > 0;
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (8,63): error CS0165: Use of unassigned local variable 'x1'
                //     bool Test1 { get; } = a && TakeOutParam(3, out int x1) || x1 > 0;
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(8, 63)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void PropertyInitializers_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(new X().Test1);
    }

    int Test1 { get; } = TakeOutParam(1, out int x1) ? Test2(((System.Func<int>)(() => x1++))(), ref x1) : -1; 

    static int Test2(object a, ref int x)
    {
        System.Console.WriteLine(x);
        x++;
        return x;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"2
3");
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [ConditionalFact(typeof(DesktopOnly), Reason = "https://github.com/dotnet/roslyn/issues/28026")]
        public void Scope_Query_01()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        var res = from x in new[] { TakeOutParam(1, out var y1) ? y1 : 0, y1}
                  select x + y1;

        Dummy(y1); 
    }

    void Test2()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y2) ? y2 : 0}
                  from x2 in new[] { TakeOutParam(x1, out var z2) ? z2 : 0, z2, y2}
                  select x1 + x2 + y2 + 
                         z2;

        Dummy(z2); 
    }

    void Test3()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y3) ? y3 : 0}
                  let x2 = TakeOutParam(x1, out var z3) && z3 > 0 && y3 < 0 
                  select new { x1, x2, y3,
                               z3};

        Dummy(z3); 
    }

    void Test4()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y4) ? y4 : 0}
                  join x2 in new[] { TakeOutParam(2, out var z4) ? z4 : 0, z4, y4}
                            on x1 + y4 + z4 + (TakeOutParam(3, out var u4) ? u4 : 0) + 
                                  v4 
                               equals x2 + y4 + z4 + (TakeOutParam(4, out var v4) ? v4 : 0) +
                                  u4 
                  select new { x1, x2, y4, z4, 
                               u4, v4 };

        Dummy(z4); 
        Dummy(u4); 
        Dummy(v4); 
    }

    void Test5()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y5) ? y5 : 0}
                  join x2 in new[] { TakeOutParam(2, out var z5) ? z5 : 0, z5, y5}
                            on x1 + y5 + z5 + (TakeOutParam(3, out var u5) ? u5 : 0) + 
                                  v5 
                               equals x2 + y5 + z5 + (TakeOutParam(4, out var v5) ? v5 : 0) +
                                  u5 
                  into g
                  select new { x1, y5, z5, g,
                               u5, v5 };

        Dummy(z5); 
        Dummy(u5); 
        Dummy(v5); 
    }

    void Test6()
    {
        var res = from x in new[] { TakeOutParam(1, out var y6) ? y6 : 0}
                  where x > y6 && TakeOutParam(1, out var z6) && z6 == 1
                  select x + y6 +
                         z6;

        Dummy(z6); 
    }

    void Test7()
    {
        var res = from x in new[] { TakeOutParam(1, out var y7) ? y7 : 0}
                  orderby x > y7 && TakeOutParam(1, out var z7) && z7 == 
                          u7,
                          x > y7 && TakeOutParam(1, out var u7) && u7 == 
                          z7   
                  select x + y7 +
                         z7 + u7;

        Dummy(z7); 
        Dummy(u7); 
    }

    void Test8()
    {
        var res = from x in new[] { TakeOutParam(1, out var y8) ? y8 : 0}
                  select x > y8 && TakeOutParam(1, out var z8) && z8 == 1;

        Dummy(z8); 
    }

    void Test9()
    {
        var res = from x in new[] { TakeOutParam(1, out var y9) ? y9 : 0}
                  group x > y9 && TakeOutParam(1, out var z9) && z9 == 
                        u9
                  by
                        x > y9 && TakeOutParam(1, out var u9) && u9 == 
                        z9;   

        Dummy(z9); 
        Dummy(u9); 
    }

    void Test10()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y10) ? y10 : 0}
                  from y10 in new[] { 1 }
                  select x1 + y10;
    }

    void Test11()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y11) ? y11 : 0}
                  let y11 = x1 + 1
                  select x1 + y11;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (25,26): error CS0103: The name 'z2' does not exist in the current context
                //                          z2;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(25, 26),
                // (27,15): error CS0103: The name 'z2' does not exist in the current context
                //         Dummy(z2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(27, 15),
                // (35,32): error CS0103: The name 'z3' does not exist in the current context
                //                                z3};
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z3").WithArguments("z3").WithLocation(35, 32),
                // (37,15): error CS0103: The name 'z3' does not exist in the current context
                //         Dummy(z3); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z3").WithArguments("z3").WithLocation(37, 15),
                // (45,35): error CS0103: The name 'v4' does not exist in the current context
                //                                   v4 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(45, 35),
                // (47,35): error CS1938: The name 'u4' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                //                                   u4 
                Diagnostic(ErrorCode.ERR_QueryInnerKey, "u4").WithArguments("u4").WithLocation(47, 35),
                // (49,32): error CS0103: The name 'u4' does not exist in the current context
                //                                u4, v4 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(49, 32),
                // (49,36): error CS0103: The name 'v4' does not exist in the current context
                //                                u4, v4 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(49, 36),
                // (52,15): error CS0103: The name 'u4' does not exist in the current context
                //         Dummy(u4); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(52, 15),
                // (53,15): error CS0103: The name 'v4' does not exist in the current context
                //         Dummy(v4); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(53, 15),
                // (61,35): error CS0103: The name 'v5' does not exist in the current context
                //                                   v5 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(61, 35),
                // (63,35): error CS1938: The name 'u5' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                //                                   u5 
                Diagnostic(ErrorCode.ERR_QueryInnerKey, "u5").WithArguments("u5").WithLocation(63, 35),
                // (66,32): error CS0103: The name 'u5' does not exist in the current context
                //                                u5, v5 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(66, 32),
                // (66,36): error CS0103: The name 'v5' does not exist in the current context
                //                                u5, v5 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(66, 36),
                // (69,15): error CS0103: The name 'u5' does not exist in the current context
                //         Dummy(u5); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(69, 15),
                // (70,15): error CS0103: The name 'v5' does not exist in the current context
                //         Dummy(v5); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(70, 15),
                // (78,26): error CS0103: The name 'z6' does not exist in the current context
                //                          z6;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z6").WithArguments("z6").WithLocation(78, 26),
                // (80,15): error CS0103: The name 'z6' does not exist in the current context
                //         Dummy(z6); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z6").WithArguments("z6").WithLocation(80, 15),
                // (87,27): error CS0103: The name 'u7' does not exist in the current context
                //                           u7,
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(87, 27),
                // (89,27): error CS0103: The name 'z7' does not exist in the current context
                //                           z7   
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(89, 27),
                // (91,26): error CS0103: The name 'z7' does not exist in the current context
                //                          z7 + u7;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(91, 26),
                // (91,31): error CS0103: The name 'u7' does not exist in the current context
                //                          z7 + u7;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(91, 31),
                // (93,15): error CS0103: The name 'z7' does not exist in the current context
                //         Dummy(z7); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(93, 15),
                // (94,15): error CS0103: The name 'u7' does not exist in the current context
                //         Dummy(u7); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(94, 15),
                // (102,15): error CS0103: The name 'z8' does not exist in the current context
                //         Dummy(z8); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z8").WithArguments("z8").WithLocation(102, 15),
                // (112,25): error CS0103: The name 'z9' does not exist in the current context
                //                         z9;   
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z9").WithArguments("z9").WithLocation(112, 25),
                // (109,25): error CS0103: The name 'u9' does not exist in the current context
                //                         u9
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u9").WithArguments("u9").WithLocation(109, 25),
                // (114,15): error CS0103: The name 'z9' does not exist in the current context
                //         Dummy(z9); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z9").WithArguments("z9").WithLocation(114, 15),
                // (115,15): error CS0103: The name 'u9' does not exist in the current context
                //         Dummy(u9); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u9").WithArguments("u9").WithLocation(115, 15),
                // (121,24): error CS1931: The range variable 'y10' conflicts with a previous declaration of 'y10'
                //                   from y10 in new[] { 1 }
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y10").WithArguments("y10").WithLocation(121, 24),
                // (128,23): error CS1931: The range variable 'y11' conflicts with a previous declaration of 'y11'
                //                   let y11 = x1 + 1
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y11").WithArguments("y11").WithLocation(128, 23)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var y1Decl = GetOutVarDeclarations(tree, "y1").Single();
            var y1Ref = GetReferences(tree, "y1").ToArray();
            Assert.Equal(4, y1Ref.Length);
            VerifyModelForOutVar(model, y1Decl, y1Ref);

            var y2Decl = GetOutVarDeclarations(tree, "y2").Single();
            var y2Ref = GetReferences(tree, "y2").ToArray();
            Assert.Equal(3, y2Ref.Length);
            VerifyModelForOutVar(model, y2Decl, y2Ref);

            var z2Decl = GetOutVarDeclarations(tree, "z2").Single();
            var z2Ref = GetReferences(tree, "z2").ToArray();
            Assert.Equal(4, z2Ref.Length);
            VerifyModelForOutVar(model, z2Decl, z2Ref[0], z2Ref[1]);
            VerifyNotInScope(model, z2Ref[2]);
            VerifyNotInScope(model, z2Ref[3]);

            var y3Decl = GetOutVarDeclarations(tree, "y3").Single();
            var y3Ref = GetReferences(tree, "y3").ToArray();
            Assert.Equal(3, y3Ref.Length);
            VerifyModelForOutVar(model, y3Decl, y3Ref);

            var z3Decl = GetOutVarDeclarations(tree, "z3").Single();
            var z3Ref = GetReferences(tree, "z3").ToArray();
            Assert.Equal(3, z3Ref.Length);
            VerifyModelForOutVar(model, z3Decl, z3Ref[0]);
            VerifyNotInScope(model, z3Ref[1]);
            VerifyNotInScope(model, z3Ref[2]);

            var y4Decl = GetOutVarDeclarations(tree, "y4").Single();
            var y4Ref = GetReferences(tree, "y4").ToArray();
            Assert.Equal(5, y4Ref.Length);
            VerifyModelForOutVar(model, y4Decl, y4Ref);

            var z4Decl = GetOutVarDeclarations(tree, "z4").Single();
            var z4Ref = GetReferences(tree, "z4").ToArray();
            Assert.Equal(6, z4Ref.Length);
            VerifyModelForOutVar(model, z4Decl, z4Ref);

            var u4Decl = GetOutVarDeclarations(tree, "u4").Single();
            var u4Ref = GetReferences(tree, "u4").ToArray();
            Assert.Equal(4, u4Ref.Length);
            VerifyModelForOutVar(model, u4Decl, u4Ref[0]);
            VerifyNotInScope(model, u4Ref[1]);
            VerifyNotInScope(model, u4Ref[2]);
            VerifyNotInScope(model, u4Ref[3]);

            var v4Decl = GetOutVarDeclarations(tree, "v4").Single();
            var v4Ref = GetReferences(tree, "v4").ToArray();
            Assert.Equal(4, v4Ref.Length);
            VerifyNotInScope(model, v4Ref[0]);
            VerifyModelForOutVar(model, v4Decl, v4Ref[1]);
            VerifyNotInScope(model, v4Ref[2]);
            VerifyNotInScope(model, v4Ref[3]);

            var y5Decl = GetOutVarDeclarations(tree, "y5").Single();
            var y5Ref = GetReferences(tree, "y5").ToArray();
            Assert.Equal(5, y5Ref.Length);
            VerifyModelForOutVar(model, y5Decl, y5Ref);

            var z5Decl = GetOutVarDeclarations(tree, "z5").Single();
            var z5Ref = GetReferences(tree, "z5").ToArray();
            Assert.Equal(6, z5Ref.Length);
            VerifyModelForOutVar(model, z5Decl, z5Ref);

            var u5Decl = GetOutVarDeclarations(tree, "u5").Single();
            var u5Ref = GetReferences(tree, "u5").ToArray();
            Assert.Equal(4, u5Ref.Length);
            VerifyModelForOutVar(model, u5Decl, u5Ref[0]);
            VerifyNotInScope(model, u5Ref[1]);
            VerifyNotInScope(model, u5Ref[2]);
            VerifyNotInScope(model, u5Ref[3]);

            var v5Decl = GetOutVarDeclarations(tree, "v5").Single();
            var v5Ref = GetReferences(tree, "v5").ToArray();
            Assert.Equal(4, v5Ref.Length);
            VerifyNotInScope(model, v5Ref[0]);
            VerifyModelForOutVar(model, v5Decl, v5Ref[1]);
            VerifyNotInScope(model, v5Ref[2]);
            VerifyNotInScope(model, v5Ref[3]);

            var y6Decl = GetOutVarDeclarations(tree, "y6").Single();
            var y6Ref = GetReferences(tree, "y6").ToArray();
            Assert.Equal(3, y6Ref.Length);
            VerifyModelForOutVar(model, y6Decl, y6Ref);

            var z6Decl = GetOutVarDeclarations(tree, "z6").Single();
            var z6Ref = GetReferences(tree, "z6").ToArray();
            Assert.Equal(3, z6Ref.Length);
            VerifyModelForOutVar(model, z6Decl, z6Ref[0]);
            VerifyNotInScope(model, z6Ref[1]);
            VerifyNotInScope(model, z6Ref[2]);

            var y7Decl = GetOutVarDeclarations(tree, "y7").Single();
            var y7Ref = GetReferences(tree, "y7").ToArray();
            Assert.Equal(4, y7Ref.Length);
            VerifyModelForOutVar(model, y7Decl, y7Ref);

            var z7Decl = GetOutVarDeclarations(tree, "z7").Single();
            var z7Ref = GetReferences(tree, "z7").ToArray();
            Assert.Equal(4, z7Ref.Length);
            VerifyModelForOutVar(model, z7Decl, z7Ref[0]);
            VerifyNotInScope(model, z7Ref[1]);
            VerifyNotInScope(model, z7Ref[2]);
            VerifyNotInScope(model, z7Ref[3]);

            var u7Decl = GetOutVarDeclarations(tree, "u7").Single();
            var u7Ref = GetReferences(tree, "u7").ToArray();
            Assert.Equal(4, u7Ref.Length);
            VerifyNotInScope(model, u7Ref[0]);
            VerifyModelForOutVar(model, u7Decl, u7Ref[1]);
            VerifyNotInScope(model, u7Ref[2]);
            VerifyNotInScope(model, u7Ref[3]);

            var y8Decl = GetOutVarDeclarations(tree, "y8").Single();
            var y8Ref = GetReferences(tree, "y8").ToArray();
            Assert.Equal(2, y8Ref.Length);
            VerifyModelForOutVar(model, y8Decl, y8Ref);

            var z8Decl = GetOutVarDeclarations(tree, "z8").Single();
            var z8Ref = GetReferences(tree, "z8").ToArray();
            Assert.Equal(2, z8Ref.Length);
            VerifyModelForOutVar(model, z8Decl, z8Ref[0]);
            VerifyNotInScope(model, z8Ref[1]);

            var y9Decl = GetOutVarDeclarations(tree, "y9").Single();
            var y9Ref = GetReferences(tree, "y9").ToArray();
            Assert.Equal(3, y9Ref.Length);
            VerifyModelForOutVar(model, y9Decl, y9Ref);

            var z9Decl = GetOutVarDeclarations(tree, "z9").Single();
            var z9Ref = GetReferences(tree, "z9").ToArray();
            Assert.Equal(3, z9Ref.Length);
            VerifyModelForOutVar(model, z9Decl, z9Ref[0]);
            VerifyNotInScope(model, z9Ref[1]);
            VerifyNotInScope(model, z9Ref[2]);

            var u9Decl = GetOutVarDeclarations(tree, "u9").Single();
            var u9Ref = GetReferences(tree, "u9").ToArray();
            Assert.Equal(3, u9Ref.Length);
            VerifyNotInScope(model, u9Ref[0]);
            VerifyModelForOutVar(model, u9Decl, u9Ref[1]);
            VerifyNotInScope(model, u9Ref[2]);

            var y10Decl = GetOutVarDeclarations(tree, "y10").Single();
            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyModelForOutVar(model, y10Decl, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y11Decl = GetOutVarDeclarations(tree, "y11").Single();
            var y11Ref = GetReferences(tree, "y11").ToArray();
            Assert.Equal(2, y11Ref.Length);
            VerifyModelForOutVar(model, y11Decl, y11Ref[0]);
            VerifyNotAnOutLocal(model, y11Ref[1]);
        }

        [Fact]
        public void Scope_Query_03()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test4()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y4) ? y4 : 0}
                  select x1 into x1
                  join x2 in new[] { TakeOutParam(2, out var z4) ? z4 : 0, z4, y4}
                            on x1 + y4 + z4 + (TakeOutParam(3, out var u4) ? u4 : 0) + 
                                  v4 
                               equals x2 + y4 + z4 + (TakeOutParam(4, out var v4) ? v4 : 0) +
                                  u4 
                  select new { x1, x2, y4, z4, 
                               u4, v4 };

        Dummy(z4); 
        Dummy(u4); 
        Dummy(v4); 
    }

    void Test5()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y5) ? y5 : 0}
                  select x1 into x1
                  join x2 in new[] { TakeOutParam(2, out var z5) ? z5 : 0, z5, y5}
                            on x1 + y5 + z5 + (TakeOutParam(3, out var u5) ? u5 : 0) + 
                                  v5 
                               equals x2 + y5 + z5 + (TakeOutParam(4 , out var v5) ? v5 : 0) +
                                  u5 
                  into g
                  select new { x1, y5, z5, g,
                               u5, v5 };

        Dummy(z5); 
        Dummy(u5); 
        Dummy(v5); 
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (18,35): error CS0103: The name 'v4' does not exist in the current context
                //                                   v4 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(18, 35),
                // (20,35): error CS1938: The name 'u4' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                //                                   u4 
                Diagnostic(ErrorCode.ERR_QueryInnerKey, "u4").WithArguments("u4").WithLocation(20, 35),
                // (22,32): error CS0103: The name 'u4' does not exist in the current context
                //                                u4, v4 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(22, 32),
                // (22,36): error CS0103: The name 'v4' does not exist in the current context
                //                                u4, v4 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(22, 36),
                // (25,15): error CS0103: The name 'u4' does not exist in the current context
                //         Dummy(u4); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(25, 15),
                // (26,15): error CS0103: The name 'v4' does not exist in the current context
                //         Dummy(v4); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(26, 15),
                // (35,35): error CS0103: The name 'v5' does not exist in the current context
                //                                   v5 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(35, 35),
                // (37,35): error CS1938: The name 'u5' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                //                                   u5 
                Diagnostic(ErrorCode.ERR_QueryInnerKey, "u5").WithArguments("u5").WithLocation(37, 35),
                // (40,32): error CS0103: The name 'u5' does not exist in the current context
                //                                u5, v5 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(40, 32),
                // (40,36): error CS0103: The name 'v5' does not exist in the current context
                //                                u5, v5 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(40, 36),
                // (43,15): error CS0103: The name 'u5' does not exist in the current context
                //         Dummy(u5); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(43, 15),
                // (44,15): error CS0103: The name 'v5' does not exist in the current context
                //         Dummy(v5); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(44, 15)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var y4Decl = GetOutVarDeclarations(tree, "y4").Single();
            var y4Ref = GetReferences(tree, "y4").ToArray();
            Assert.Equal(5, y4Ref.Length);
            VerifyModelForOutVar(model, y4Decl, y4Ref);

            var z4Decl = GetOutVarDeclarations(tree, "z4").Single();
            var z4Ref = GetReferences(tree, "z4").ToArray();
            Assert.Equal(6, z4Ref.Length);
            VerifyModelForOutVar(model, z4Decl, z4Ref);

            var u4Decl = GetOutVarDeclarations(tree, "u4").Single();
            var u4Ref = GetReferences(tree, "u4").ToArray();
            Assert.Equal(4, u4Ref.Length);
            VerifyModelForOutVar(model, u4Decl, u4Ref[0]);
            VerifyNotInScope(model, u4Ref[1]);
            VerifyNotInScope(model, u4Ref[2]);
            VerifyNotInScope(model, u4Ref[3]);

            var v4Decl = GetOutVarDeclarations(tree, "v4").Single();
            var v4Ref = GetReferences(tree, "v4").ToArray();
            Assert.Equal(4, v4Ref.Length);
            VerifyNotInScope(model, v4Ref[0]);
            VerifyModelForOutVar(model, v4Decl, v4Ref[1]);
            VerifyNotInScope(model, v4Ref[2]);
            VerifyNotInScope(model, v4Ref[3]);

            var y5Decl = GetOutVarDeclarations(tree, "y5").Single();
            var y5Ref = GetReferences(tree, "y5").ToArray();
            Assert.Equal(5, y5Ref.Length);
            VerifyModelForOutVar(model, y5Decl, y5Ref);

            var z5Decl = GetOutVarDeclarations(tree, "z5").Single();
            var z5Ref = GetReferences(tree, "z5").ToArray();
            Assert.Equal(6, z5Ref.Length);
            VerifyModelForOutVar(model, z5Decl, z5Ref);

            var u5Decl = GetOutVarDeclarations(tree, "u5").Single();
            var u5Ref = GetReferences(tree, "u5").ToArray();
            Assert.Equal(4, u5Ref.Length);
            VerifyModelForOutVar(model, u5Decl, u5Ref[0]);
            VerifyNotInScope(model, u5Ref[1]);
            VerifyNotInScope(model, u5Ref[2]);
            VerifyNotInScope(model, u5Ref[3]);

            var v5Decl = GetOutVarDeclarations(tree, "v5").Single();
            var v5Ref = GetReferences(tree, "v5").ToArray();
            Assert.Equal(4, v5Ref.Length);
            VerifyNotInScope(model, v5Ref[0]);
            VerifyModelForOutVar(model, v5Decl, v5Ref[1]);
            VerifyNotInScope(model, v5Ref[2]);
            VerifyNotInScope(model, v5Ref[3]);
        }

        [Fact]
        [WorkItem(10466, "https://github.com/dotnet/roslyn/issues/10466")]
        public void Scope_Query_05()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        int y1 = 0, y2 = 0, y3 = 0, y4 = 0, y5 = 0, y6 = 0, y7 = 0, y8 = 0, y9 = 0, y10 = 0, y11 = 0, y12 = 0;

        var res = from x1 in new[] { TakeOutParam(1, out var y1) ? y1 : 0}
                  from x2 in new[] { TakeOutParam(2, out var y2) ? y2 : 0}
                  join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                       on TakeOutParam(4, out var y4) ? y4 : 0
                          equals TakeOutParam(5, out var y5) ? y5 : 0
                  where TakeOutParam(6, out var y6) && y6 == 1
                  orderby TakeOutParam(7, out var y7) && y7 > 0, 
                          TakeOutParam(8, out var y8) && y8 > 0 
                  group TakeOutParam(9, out var y9) && y9 > 0 
                  by TakeOutParam(10, out var y10) && y10 > 0
                  into g
                  let x11 = TakeOutParam(11, out var y11) && y11 > 0
                  select TakeOutParam(12, out var y12) && y12 > 0
                  into s
                  select y1 + y2 + y3 + y4 + y5 + y6 + y7 + y8 + y9 + y10 + y11 + y12 + (TakeOutParam(13, out var y13) ? y13 : 0);

        Dummy(y1, y2, y3, y4, y5, y6, y7, y8, y9, y10, y11, y12); 
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (16,62): error CS0128: A local variable or function named 'y1' is already defined in this scope
                //         var res = from x1 in new[] { TakeOutParam(1, out var y1) ? y1 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y1").WithArguments("y1").WithLocation(16, 62),
                // (18,62): error CS0128: A local variable or function named 'y3' is already defined in this scope
                //                   join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y3").WithArguments("y3").WithLocation(18, 62)
                );

            compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_3);
            compilation.VerifyDiagnostics(
                // (16,62): error CS0128: A local variable or function named 'y1' is already defined in this scope
                //         var res = from x1 in new[] { TakeOutParam(1, out var y1) ? y1 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y1").WithArguments("y1").WithLocation(16, 62),
                // (17,62): error CS0136: A local or parameter named 'y2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   from x2 in new[] { TakeOutParam(2, out var y2) ? y2 : 0}
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y2").WithArguments("y2").WithLocation(17, 62),
                // (18,62): error CS0128: A local variable or function named 'y3' is already defined in this scope
                //                   join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y3").WithArguments("y3").WithLocation(18, 62),
                // (19,51): error CS0136: A local or parameter named 'y4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                        on TakeOutParam(4, out var y4) ? y4 : 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y4").WithArguments("y4").WithLocation(19, 51),
                // (20,58): error CS0136: A local or parameter named 'y5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                           equals TakeOutParam(5, out var y5) ? y5 : 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y5").WithArguments("y5").WithLocation(20, 58),
                // (21,49): error CS0136: A local or parameter named 'y6' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   where TakeOutParam(6, out var y6) && y6 == 1
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y6").WithArguments("y6").WithLocation(21, 49),
                // (22,51): error CS0136: A local or parameter named 'y7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   orderby TakeOutParam(7, out var y7) && y7 > 0, 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y7").WithArguments("y7").WithLocation(22, 51),
                // (23,51): error CS0136: A local or parameter named 'y8' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                           TakeOutParam(8, out var y8) && y8 > 0 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y8").WithArguments("y8").WithLocation(23, 51),
                // (25,47): error CS0136: A local or parameter named 'y10' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   by TakeOutParam(10, out var y10) && y10 > 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y10").WithArguments("y10").WithLocation(25, 47),
                // (24,49): error CS0136: A local or parameter named 'y9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   group TakeOutParam(9, out var y9) && y9 > 0 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y9").WithArguments("y9").WithLocation(24, 49),
                // (27,54): error CS0136: A local or parameter named 'y11' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   let x11 = TakeOutParam(11, out var y11) && y11 > 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y11").WithArguments("y11").WithLocation(27, 54),
                // (28,51): error CS0136: A local or parameter named 'y12' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   select TakeOutParam(12, out var y12) && y12 > 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y12").WithArguments("y12").WithLocation(28, 51)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i < 13; i++)
            {
                var id = "y" + i;
                var yDecl = GetOutVarDeclarations(tree, id).Single();
                var yRef = GetReferences(tree, id).ToArray();
                Assert.Equal(3, yRef.Length);

                switch (i)
                {
                    case 1:
                    case 3:
                        VerifyModelForOutVarDuplicateInSameScope(model, yDecl);
                        VerifyNotAnOutLocal(model, yRef[0]);
                        break;
                    default:
                        VerifyModelForOutVar(model, yDecl, yRef[0]);
                        break;
                }

                VerifyNotAnOutLocal(model, yRef[2]);

                switch (i)
                {
                    case 12:
                        VerifyNotAnOutLocal(model, yRef[1]);
                        break;
                    default:
                        VerifyNotAnOutLocal(model, yRef[1]);
                        break;
                }
            }

            var y13Decl = GetOutVarDeclarations(tree, "y13").Single();
            var y13Ref = GetReference(tree, "y13");
            VerifyModelForOutVar(model, y13Decl, y13Ref);
        }

        [Fact]
        [WorkItem(10466, "https://github.com/dotnet/roslyn/issues/10466")]
        public void Scope_Query_06()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        Dummy(TakeOutParam(out int y1), 
              TakeOutParam(out int y2), 
              TakeOutParam(out int y3), 
              TakeOutParam(out int y4), 
              TakeOutParam(out int y5), 
              TakeOutParam(out int y6), 
              TakeOutParam(out int y7), 
              TakeOutParam(out int y8), 
              TakeOutParam(out int y9), 
              TakeOutParam(out int y10), 
              TakeOutParam(out int y11), 
              TakeOutParam(out int y12),
                  from x1 in new[] { TakeOutParam(1, out var y1) ? y1 : 0}
                  from x2 in new[] { TakeOutParam(2, out var y2) ? y2 : 0}
                  join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                       on TakeOutParam(4, out var y4) ? y4 : 0
                          equals TakeOutParam(5, out var y5) ? y5 : 0
                  where TakeOutParam(6, out var y6) && y6 == 1
                  orderby TakeOutParam(7, out var y7) && y7 > 0, 
                          TakeOutParam(8, out var y8) && y8 > 0 
                  group TakeOutParam(9, out var y9) && y9 > 0 
                  by TakeOutParam(10, out var y10) && y10 > 0
                  into g
                  let x11 = TakeOutParam(11, out var y11) && y11 > 0
                  select TakeOutParam(12, out var y12) && y12 > 0
                  into s
                  select y1 + y2 + y3 + y4 + y5 + y6 + y7 + y8 + y9 + y10 + y11 + y12);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }

    static bool TakeOutParam(out int x) 
    {
        x = 0;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (26,62): error CS0128: A local variable or function named 'y1' is already defined in this scope
                //                   from x1 in new[] { TakeOutParam(1, out var y1) ? y1 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y1").WithArguments("y1").WithLocation(26, 62),
                // (28,62): error CS0128: A local variable or function named 'y3' is already defined in this scope
                //                   join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y3").WithArguments("y3").WithLocation(28, 62)
                );

            compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_3);
            compilation.VerifyDiagnostics(
                // (26,62): error CS0128: A local variable or function named 'y1' is already defined in this scope
                //                   from x1 in new[] { TakeOutParam(1, out var y1) ? y1 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y1").WithArguments("y1").WithLocation(26, 62),
                // (27,62): error CS0136: A local or parameter named 'y2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   from x2 in new[] { TakeOutParam(2, out var y2) ? y2 : 0}
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y2").WithArguments("y2").WithLocation(27, 62),
                // (28,62): error CS0128: A local variable or function named 'y3' is already defined in this scope
                //                   join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y3").WithArguments("y3").WithLocation(28, 62),
                // (29,51): error CS0136: A local or parameter named 'y4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                        on TakeOutParam(4, out var y4) ? y4 : 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y4").WithArguments("y4").WithLocation(29, 51),
                // (30,58): error CS0136: A local or parameter named 'y5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                           equals TakeOutParam(5, out var y5) ? y5 : 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y5").WithArguments("y5").WithLocation(30, 58),
                // (31,49): error CS0136: A local or parameter named 'y6' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   where TakeOutParam(6, out var y6) && y6 == 1
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y6").WithArguments("y6").WithLocation(31, 49),
                // (32,51): error CS0136: A local or parameter named 'y7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   orderby TakeOutParam(7, out var y7) && y7 > 0, 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y7").WithArguments("y7").WithLocation(32, 51),
                // (33,51): error CS0136: A local or parameter named 'y8' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                           TakeOutParam(8, out var y8) && y8 > 0 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y8").WithArguments("y8").WithLocation(33, 51),
                // (35,47): error CS0136: A local or parameter named 'y10' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   by TakeOutParam(10, out var y10) && y10 > 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y10").WithArguments("y10").WithLocation(35, 47),
                // (34,49): error CS0136: A local or parameter named 'y9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   group TakeOutParam(9, out var y9) && y9 > 0 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y9").WithArguments("y9").WithLocation(34, 49),
                // (37,54): error CS0136: A local or parameter named 'y11' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   let x11 = TakeOutParam(11, out var y11) && y11 > 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y11").WithArguments("y11").WithLocation(37, 54),
                // (38,51): error CS0136: A local or parameter named 'y12' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   select TakeOutParam(12, out var y12) && y12 > 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y12").WithArguments("y12").WithLocation(38, 51)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i < 13; i++)
            {
                var id = "y" + i;
                var yDecl = GetOutVarDeclarations(tree, id).ToArray();
                var yRef = GetReferences(tree, id).ToArray();
                Assert.Equal(2, yDecl.Length);
                Assert.Equal(2, yRef.Length);

                switch (i)
                {
                    case 1:
                    case 3:
                        VerifyModelForOutVar(model, yDecl[0], yRef);
                        VerifyModelForOutVarDuplicateInSameScope(model, yDecl[1]);
                        break;
                    case 12:
                        VerifyModelForOutVar(model, yDecl[0], yRef[1]);
                        VerifyModelForOutVar(model, yDecl[1], yRef[0]);
                        break;

                    default:
                        VerifyModelForOutVar(model, yDecl[0], yRef[1]);
                        VerifyModelForOutVar(model, yDecl[1], yRef[0]);
                        break;
                }
            }
        }

        [Fact]
        public void Scope_Query_07()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        Dummy(TakeOutParam(out int y3), 
                  from x1 in new[] { 0 }
                  select x1
                  into x1
                  join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                       on x1 equals x3
                  select y3);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }

    static bool TakeOutParam(out int x) 
    {
        x = 0;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (18,62): error CS0128: A local variable named 'y3' is already defined in this scope
                //                   join x3 in new[] { TakeOutParam(3, out var y3) ? y3 : 0}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y3").WithArguments("y3").WithLocation(18, 62)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            const string id = "y3";
            var yDecl = GetOutVarDeclarations(tree, id).ToArray();
            var yRef = GetReferences(tree, id).ToArray();
            Assert.Equal(2, yDecl.Length);
            Assert.Equal(2, yRef.Length);
            // Since the name is declared twice in the same scope,
            // both references are to the same declaration.
            VerifyModelForOutVar(model, yDecl[0], yRef);
            VerifyModelForOutVarDuplicateInSameScope(model, yDecl[1]);
        }

        [Fact]
        public void Scope_Query_08()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        var res = from x1 in new[] { Dummy(TakeOutParam(out var y1), 
                                           TakeOutParam(out var y2),
                                           TakeOutParam(out var y3),
                                           TakeOutParam(out var y4)
                                          ) ? 1 : 0}
                  from y1 in new[] { 1 }
                  join y2 in new[] { 0 }
                       on y1 equals y2
                  let y3 = 0
                  group y3 
                  by x1
                  into y4
                  select y4;
    }

    static bool TakeOutParam(out int x) 
    {
        x = 0;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (19,24): error CS1931: The range variable 'y1' conflicts with a previous declaration of 'y1'
                //                   from y1 in new[] { 1 }
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y1").WithArguments("y1").WithLocation(19, 24),
                // (20,24): error CS1931: The range variable 'y2' conflicts with a previous declaration of 'y2'
                //                   join y2 in new[] { 0 }
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y2").WithArguments("y2").WithLocation(20, 24),
                // (22,23): error CS1931: The range variable 'y3' conflicts with a previous declaration of 'y3'
                //                   let y3 = 0
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y3").WithArguments("y3").WithLocation(22, 23),
                // (25,24): error CS1931: The range variable 'y4' conflicts with a previous declaration of 'y4'
                //                   into y4
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y4").WithArguments("y4").WithLocation(25, 24)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i < 5; i++)
            {
                var id = "y" + i;
                var yDecl = GetOutVarDeclarations(tree, id).Single();
                var yRef = GetReferences(tree, id).Single();
                VerifyModelForOutVar(model, yDecl);
                VerifyNotAnOutLocal(model, yRef);
            }
        }

        [Fact]
        [WorkItem(10466, "https://github.com/dotnet/roslyn/issues/10466")]
        public void Scope_Query_09()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        var res = from y1 in new[] { 0 }
                  join y2 in new[] { 0 }
                       on y1 equals y2
                  let y3 = 0
                  group y3 
                  by 1
                  into y4
                  select y4 == null ? 1 : 0
                  into x2
                  join y5 in new[] { Dummy(TakeOutParam(out var y1), 
                                           TakeOutParam(out var y2),
                                           TakeOutParam(out var y3),
                                           TakeOutParam(out var y4),
                                           TakeOutParam(out var y5)
                                          ) ? 1 : 0 }
                       on x2 equals y5
                  select x2;
    }

    static bool TakeOutParam(out int x) 
    {
        x = 0;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (14,24): error CS1931: The range variable 'y1' conflicts with a previous declaration of 'y1'
                //         var res = from y1 in new[] { 0 }
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y1").WithArguments("y1").WithLocation(14, 24),
                // (15,24): error CS1931: The range variable 'y2' conflicts with a previous declaration of 'y2'
                //                   join y2 in new[] { 0 }
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y2").WithArguments("y2").WithLocation(15, 24),
                // (17,23): error CS1931: The range variable 'y3' conflicts with a previous declaration of 'y3'
                //                   let y3 = 0
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y3").WithArguments("y3").WithLocation(17, 23),
                // (20,24): error CS1931: The range variable 'y4' conflicts with a previous declaration of 'y4'
                //                   into y4
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y4").WithArguments("y4").WithLocation(20, 24),
                // (23,24): error CS1931: The range variable 'y5' conflicts with a previous declaration of 'y5'
                //                   join y5 in new[] { Dummy(TakeOutParam(out var y1), 
                Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y5").WithArguments("y5").WithLocation(23, 24)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i < 6; i++)
            {
                var id = "y" + i;
                var yDecl = GetOutVarDeclarations(tree, id).Single();
                var yRef = GetReferences(tree, id).Single();

                switch (i)
                {
                    case 4:
                        VerifyModelForOutVar(model, yDecl);
                        VerifyNotAnOutLocal(model, yRef);
                        break;
                    case 5:
                        VerifyModelForOutVar(model, yDecl);
                        VerifyNotAnOutLocal(model, yRef);
                        break;
                    default:
                        VerifyModelForOutVar(model, yDecl);
                        VerifyNotAnOutLocal(model, yRef);
                        break;
                }
            }
        }

        [Fact]
        [WorkItem(10466, "https://github.com/dotnet/roslyn/issues/10466")]
        [WorkItem(12052, "https://github.com/dotnet/roslyn/issues/12052")]
        public void Scope_Query_10()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        var res = from y1 in new[] { 0 }
                  from x2 in new[] { TakeOutParam(out var y1) ? y1 : 1 }
                  select y1;
    }

    void Test2()
    {
        var res = from y2 in new[] { 0 }
                  join x3 in new[] { 1 }
                       on TakeOutParam(out var y2) ? y2 : 0 
                       equals x3
                  select y2;
    }

    void Test3()
    {
        var res = from x3 in new[] { 0 }
                  join y3 in new[] { 1 }
                       on x3 
                       equals TakeOutParam(out var y3) ? y3 : 0
                  select y3;
    }

    void Test4()
    {
        var res = from y4 in new[] { 0 }
                  where TakeOutParam(out var y4) && y4 == 1
                  select y4;
    }

    void Test5()
    {
        var res = from y5 in new[] { 0 }
                  orderby TakeOutParam(out var y5) && y5 > 1, 
                          1 
                  select y5;
    }

    void Test6()
    {
        var res = from y6 in new[] { 0 }
                  orderby 1, 
                          TakeOutParam(out var y6) && y6 > 1 
                  select y6;
    }

    void Test7()
    {
        var res = from y7 in new[] { 0 }
                  group TakeOutParam(out var y7) && y7 == 3 
                  by y7;
    }

    void Test8()
    {
        var res = from y8 in new[] { 0 }
                  group y8 
                  by TakeOutParam(out var y8) && y8 == 3;
    }

    void Test9()
    {
        var res = from y9 in new[] { 0 }
                  let x4 = TakeOutParam(out var y9) && y9 > 0
                  select y9;
    }

    void Test10()
    {
        var res = from y10 in new[] { 0 }
                  select TakeOutParam(out var y10) && y10 > 0;
    }

    static bool TakeOutParam(out int x) 
    {
        x = 0;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            // error CS0412 is misleading and reported due to preexisting bug https://github.com/dotnet/roslyn/issues/12052
            compilation.VerifyDiagnostics(
                // (15,59): error CS0136: A local or parameter named 'y1' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   from x2 in new[] { TakeOutParam(out var y1) ? y1 : 1 }
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y1").WithArguments("y1").WithLocation(15, 59),
                // (23,48): error CS0136: A local or parameter named 'y2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                        on TakeOutParam(out var y2) ? y2 : 0 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y2").WithArguments("y2").WithLocation(23, 48),
                // (33,52): error CS0136: A local or parameter named 'y3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                        equals TakeOutParam(out var y3) ? y3 : 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y3").WithArguments("y3").WithLocation(33, 52),
                // (40,46): error CS0136: A local or parameter named 'y4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   where TakeOutParam(out var y4) && y4 == 1
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y4").WithArguments("y4").WithLocation(40, 46),
                // (47,48): error CS0136: A local or parameter named 'y5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   orderby TakeOutParam(out var y5) && y5 > 1, 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y5").WithArguments("y5").WithLocation(47, 48),
                // (56,48): error CS0136: A local or parameter named 'y6' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                           TakeOutParam(out var y6) && y6 > 1 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y6").WithArguments("y6").WithLocation(56, 48),
                // (63,46): error CS0136: A local or parameter named 'y7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   group TakeOutParam(out var y7) && y7 == 3 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y7").WithArguments("y7").WithLocation(63, 46),
                // (71,43): error CS0136: A local or parameter named 'y8' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   by TakeOutParam(out var y8) && y8 == 3;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y8").WithArguments("y8").WithLocation(71, 43),
                // (77,49): error CS0136: A local or parameter named 'y9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   let x4 = TakeOutParam(out var y9) && y9 > 0
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y9").WithArguments("y9").WithLocation(77, 49),
                // (84,47): error CS0136: A local or parameter named 'y10' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                   select TakeOutParam(out var y10) && y10 > 0;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y10").WithArguments("y10").WithLocation(84, 47)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i < 11; i++)
            {
                var id = "y" + i;
                var yDecl = GetOutVarDeclarations(tree, id).Single();
                var yRef = GetReferences(tree, id).ToArray();
                Assert.Equal(i == 10 ? 1 : 2, yRef.Length);

                switch (i)
                {
                    case 4:
                    case 6:
                        VerifyModelForOutVar(model, yDecl, yRef[0]);
                        VerifyNotAnOutLocal(model, yRef[1]);
                        break;
                    case 8:
                        VerifyModelForOutVar(model, yDecl, yRef[1]);
                        VerifyNotAnOutLocal(model, yRef[0]);
                        break;
                    case 10:
                        VerifyModelForOutVar(model, yDecl, yRef[0]);
                        break;
                    default:
                        VerifyModelForOutVar(model, yDecl, yRef[0]);
                        VerifyNotAnOutLocal(model, yRef[1]);
                        break;
                }
            }
        }

        [Fact]
        public void Scope_Query_11()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        var res = from x1 in new [] { 1 } 
                  where Dummy(TakeOutParam(x1, out var y1), 
                              from x2 in new [] { y1 } 
                              where TakeOutParam(x1, out var y1)
                              select x2) 
                  select x1;
    }

    void Test2()
    {
        var res = from x1 in new [] { 1 } 
                  where Dummy(TakeOutParam(x1, out var y2), 
                              TakeOutParam(x1 + 1, out var y2))
                  select x1;
    }

    void Test3()
    {
        var res = from x1 in new [] { 1 } 
                  where TakeOutParam(out int y3, y3)
                  select x1;
    }

    void Test4()
    {
        var res = from x1 in new [] { 1 } 
                  where TakeOutParam(out var y4, y4)
                  select x1;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
    static bool TakeOutParam(out int x, int y) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (26,60): error CS0128: A local variable or function named 'y2' is already defined in this scope
                //                               TakeOutParam(x1 + 1, out var y2))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y2").WithArguments("y2").WithLocation(26, 60),
                // (33,50): error CS0165: Use of unassigned local variable 'y3'
                //                   where TakeOutParam(out int y3, y3)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "y3").WithArguments("y3").WithLocation(33, 50),
                // (40,50): error CS8196: Reference to an implicitly-typed out variable 'y4' is not permitted in this location.
                //                   where TakeOutParam(out var y4, y4)
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableUsedInForbiddenZone, "y4").WithArguments("y4").WithLocation(40, 50)
                );

            compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_3);
            compilation.VerifyDiagnostics(
                // (17,62): error CS0136: A local or parameter named 'y1' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                               where TakeOutParam(x1, out var y1)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "y1").WithArguments("y1").WithLocation(17, 62),
                // (26,60): error CS0128: A local variable or function named 'y2' is already defined in this scope
                //                               TakeOutParam(x1 + 1, out var y2))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "y2").WithArguments("y2").WithLocation(26, 60),
                // (33,50): error CS0165: Use of unassigned local variable 'y3'
                //                   where TakeOutParam(out int y3, y3)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "y3").WithArguments("y3").WithLocation(33, 50),
                // (40,50): error CS8196: Reference to an implicitly-typed out variable 'y4' is not permitted in this location.
                //                   where TakeOutParam(out var y4, y4)
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableUsedInForbiddenZone, "y4").WithArguments("y4").WithLocation(40, 50)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var y1Decl = GetOutVarDeclarations(tree, "y1").ToArray();
            var y1Ref = GetReferences(tree, "y1").Single();
            Assert.Equal(2, y1Decl.Length);
            VerifyModelForOutVar(model, y1Decl[0], y1Ref);
            VerifyModelForOutVar(model, y1Decl[1]);

            var y2Decl = GetOutVarDeclarations(tree, "y2").ToArray();
            Assert.Equal(2, y2Decl.Length);
            VerifyModelForOutVar(model, y2Decl[0]);
            VerifyModelForOutVarDuplicateInSameScope(model, y2Decl[1]);

            var y3Decl = GetOutVarDeclarations(tree, "y3").Single();
            var y3Ref = GetReferences(tree, "y3").Single();
            VerifyModelForOutVarWithoutDataFlow(model, y3Decl, y3Ref);

            var y4Decl = GetOutVarDeclarations(tree, "y4").Single();
            var y4Ref = GetReferences(tree, "y4").Single();
            VerifyModelForOutVarWithoutDataFlow(model, y4Decl, y4Ref);
        }

        [ConditionalFact(typeof(WindowsDesktopOnly), Reason = "https://github.com/dotnet/roslyn/issues/28026")]
        public void Query_01()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
        Test1();
    }

    static void Test1()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y1) && Print(y1) ? 1 : 0}
                  from x2 in new[] { TakeOutParam(2, out var y2) && Print(y2) ? 1 : 0}
                  join x3 in new[] { TakeOutParam(3, out var y3) && Print(y3) ? 1 : 0}
                       on TakeOutParam(4, out var y4) && Print(y4) ? 1 : 0
                          equals TakeOutParam(5, out var y5) && Print(y5) ? 1 : 0
                  where TakeOutParam(6, out var y6) && Print(y6)
                  orderby TakeOutParam(7, out var y7) && Print(y7), 
                          TakeOutParam(8, out var y8) && Print(y8) 
                  group TakeOutParam(9, out var y9) && Print(y9) 
                  by TakeOutParam(10, out var y10) && Print(y10)
                  into g
                  let x11 = TakeOutParam(11, out var y11) && Print(y11)
                  select TakeOutParam(12, out var y12) && Print(y12);

        res.ToArray(); 
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }

    static bool Print(object x) 
    {
        System.Console.WriteLine(x);
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics();

            CompileAndVerify(compilation, expectedOutput:
@"1
3
5
2
4
6
7
8
10
9
11
12
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i < 13; i++)
            {
                var id = "y" + i;
                var yDecl = GetOutVarDeclarations(tree, id).Single();
                var yRef = GetReferences(tree, id).Single();
                VerifyModelForOutVar(model, yDecl, yRef);

                Assert.Equal("System.Int32", ((ILocalSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(GetVariableDesignation(yDecl))).Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void Query_02()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
        Test1();
    }

    static void Test1()
    {
        var res = from x1 in new[] { TakeOutParam(1, out var y1) && Print(y1) ? 2 : 0}
                  select Print(x1);

        res.ToArray(); 
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }

    static bool Print(object x) 
    {
        System.Console.WriteLine(x);
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"1
2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yDecl = GetOutVarDeclarations(tree, "y1").Single();
            var yRef = GetReferences(tree, "y1").Single();
            VerifyModelForOutVar(model, yDecl, yRef);
        }

        [Fact]
        public void Query_03()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    static void Test1()
    {
        var res = from a in new[] { true }
                  select a && TakeOutParam(3, out int x1) || x1 > 0;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (13,62): error CS0165: Use of unassigned local variable 'x1'
                //                   select a && TakeOutParam(3, out int x1) || x1 > 0;
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(13, 62)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            compilation.VerifyOperationTree(x1Decl, expectedOperationTree:
@"
IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32) (Syntax: 'int x1')
  ILocalReferenceOperation: x1 (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x1')
");
        }

        [Fact]
        public void Query_04()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static int Test1()
    {
        var res = from a in new[] { 1 }
                  select TakeOutParam(a, out int x1) ? Test2(((System.Func<int>)(() => x1++))(), ref x1) : -1;

        return res.Single(); 
    }

    static int Test2(object a, ref int x)
    {
        System.Console.WriteLine(x);
        x++;
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"2
3");
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void Query_05()
        {
            var source =
@"
using System.Linq;

public class X
{
    public static void Main()
    {
    }

    static void Test1()
    {
        var res = from a in (new[] { 1 }).AsQueryable()
                  select TakeOutParam(a, out int x1);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (13,46): error CS8198: An expression tree may not contain an out argument variable declaration.
                //                   select TakeOutParam(a, out int x1);
                Diagnostic(ErrorCode.ERR_ExpressionTreeContainsOutVariable, "int x1").WithLocation(13, 46)
                );
        }

        [Fact]
        public void Scope_ReturnStatement_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) { return null; }

    object Test1()
    {
        return Dummy(TakeOutParam(true, out var x1), x1);
        {
            return Dummy(TakeOutParam(true, out var x1), x1);
        }
        return Dummy(TakeOutParam(true, out var x1), x1);
    }

    object Test2()
    {
        return Dummy(x2, TakeOutParam(true, out var x2));
    }

    object Test3(int x3)
    {
        return Dummy(TakeOutParam(true, out var x3), x3);
    }

    object Test4()
    {
        var x4 = 11;
        Dummy(x4);
        return Dummy(TakeOutParam(true, out var x4), x4);
    }

    object Test5()
    {
        return Dummy(TakeOutParam(true, out var x5), x5);
        var x5 = 11;
        Dummy(x5);
    }

    //object Test6()
    //{
    //    let x6 = 11;
    //    Dummy(x6);
    //    return Dummy(TakeOutParam(true, out var x6), x6);
    //}

    //object Test7()
    //{
    //    return Dummy(TakeOutParam(true, out var x7), x7);
    //    let x7 = 11;
    //    Dummy(x7);
    //}

    object Test8()
    {
        return Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
    }

    object Test9(bool y9)
    {
        if (y9)
            return Dummy(TakeOutParam(true, out var x9), x9);
        return null;
    }
    System.Func<object> Test10(bool y10)
    {
        return () =>
                {
                    if (y10)
                        return Dummy(TakeOutParam(true, out var x10), x10);
                    return null;};
    }

    object Test11()
    {
        Dummy(x11);
        return Dummy(TakeOutParam(true, out var x11), x11);
    }

    object Test12()
    {
        return Dummy(TakeOutParam(true, out var x12), x12);
        Dummy(x12);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (14,53): error CS0136: A local or parameter named 'x1' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             return Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x1").WithArguments("x1").WithLocation(14, 53),
                // (16,49): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //         return Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(16, 49),
                // (14,13): warning CS0162: Unreachable code detected
                //             return Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "return").WithLocation(14, 13),
                // (21,22): error CS0841: Cannot use local variable 'x2' before it is declared
                //         return Dummy(x2, TakeOutParam(true, out var x2));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x2").WithArguments("x2").WithLocation(21, 22),
                // (26,49): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         return Dummy(TakeOutParam(true, out var x3), x3);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(26, 49),
                // (33,49): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //         return Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(33, 49),
                // (39,13): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //         var x5 = 11;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(39, 13),
                // (39,9): warning CS0162: Unreachable code detected
                //         var x5 = 11;
                Diagnostic(ErrorCode.WRN_UnreachableCode, "var").WithLocation(39, 9),
                // (39,13): warning CS0219: The variable 'x5' is assigned but its value is never used
                //         var x5 = 11;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x5").WithArguments("x5").WithLocation(39, 13),
                // (59,86): error CS0128: A local variable or function named 'x8' is already defined in this scope
                //         return Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(59, 86),
                // (79,15): error CS0841: Cannot use local variable 'x11' before it is declared
                //         Dummy(x11);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x11").WithArguments("x11").WithLocation(79, 15),
                // (86,9): warning CS0162: Unreachable code detected
                //         Dummy(x12);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "Dummy").WithLocation(86, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl[2]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(2, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Decl.Length);
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl[0], x8Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl[1]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReferences(tree, "x9").Single();
            VerifyModelForOutVar(model, x9Decl, x9Ref);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            VerifyModelForOutVar(model, x10Decl, x10Ref);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(2, x11Ref.Length);
            VerifyModelForOutVar(model, x11Decl, x11Ref);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(2, x12Ref.Length);
            VerifyModelForOutVar(model, x12Decl, x12Ref);
        }

        [Fact]
        public void Scope_ReturnStatement_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    int Dummy(params object[] x) { return 0;}

    int Test1(bool val)
    {
        if (val)
            return Dummy(TakeOutParam(true, out var x1));

        x1++;
        return 0;
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (15,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(15, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0]);
            VerifyNotInScope(model, x1Ref[0]);
        }

        [Fact]
        public void Scope_ReturnStatement_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (ReturnStatementSyntax)SyntaxFactory.ParseStatement(@"
return Dummy(TakeOutParam(true, out var x1), x1);
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Return_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test();
    }

    static object Test()
    {
        return Dummy(TakeOutParam(""return"", out var x1), x1);
    }

    static object Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new object();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"return");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Return_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(true);
        Test(false);
    }

    static object Test(bool val)
    {
        if (val)
            return Dummy(TakeOutParam(""return 1"", out var x2), x2);

        if (!val)
        {
            return Dummy(TakeOutParam(""return 2"", out var x2), x2);
        }

        return null;
    }

    static object Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new object();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"return 1
return 2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref[0]);
            VerifyModelForOutVar(model, x2Decl[1], x2Ref[1]);
        }

        [Fact]
        public void Scope_Switch_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        switch (TakeOutParam(1, out var x1) ? x1 : 0)
        {
            case 0:
                Dummy(x1, 0);
                break;
        }

        Dummy(x1, 1);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        switch (TakeOutParam(4, out var x4) ? x4 : 0)
        {
            case 4:
                Dummy(x4);
                break;
        }
    }

    void Test5(int x5)
    {
        switch (TakeOutParam(5, out var x5) ? x5 : 0)
        {
            case 5:
                Dummy(x5);
                break;
        }
    }

    void Test6()
    {
        switch (x6 + (TakeOutParam(6, out var x6) ? x6 : 0))
        {
            case 6:
                Dummy(x6);
                break;
        }
    }

    void Test7()
    {
        switch (TakeOutParam(7, out var x7) ? x7 : 0)
        {
            case 7:
                var x7 = 12;
                Dummy(x7);
                break;
        }
    }

    void Test9()
    {
        switch (TakeOutParam(9, out var x9) ? x9 : 0)
        {
            case 9:
                Dummy(x9, 0);
                switch (TakeOutParam(9, out var x9) ? x9 : 0)
                {
                    case 9:
                        Dummy(x9, 1);
                        break;
                }
                break;
        }

    }

    void Test10()
    {
        switch (y10 + (TakeOutParam(10, out var x10) ? x10 : 0))
        {
            case 10:
                var y10 = 12;
                Dummy(y10);
                break;
        }
    }

    //void Test11()
    //{
    //    switch (y11 + (TakeOutParam(11, out var x11) ? x11 : 0))
    //    {
    //        case 11:
    //            let y11 = 12;
    //            Dummy(y11);
    //            break;
    //    }
    //}

    void Test14()
    {
        switch (Dummy(TakeOutParam(1, out var x14), 
                  TakeOutParam(2, out var x14), 
                  x14) ? 1 : 0)
        {
            case 0:
                Dummy(x14);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (27,41): error CS0128: A local variable named 'x4' is already defined in this scope
                //         switch (TakeOutParam(4, out var x4) ? x4 : 0)
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(27, 41),
                // (37,41): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         switch (TakeOutParam(5, out var x5) ? x5 : 0)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(37, 41),
                // (47,17): error CS0841: Cannot use local variable 'x6' before it is declared
                //         switch (x6 + (TakeOutParam(6, out var x6) ? x6 : 0))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(47, 17),
                // (60,21): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                 var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(60, 21),
                // (71,23): error CS0841: Cannot use local variable 'x9' before it is declared
                //                 Dummy(x9, 0);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x9").WithArguments("x9").WithLocation(71, 23),
                // (72,49): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                 switch (TakeOutParam(9, out var x9) ? x9 : 0)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(72, 49),
                // (85,17): error CS0103: The name 'y10' does not exist in the current context
                //         switch (y10 + (TakeOutParam(10, out var x10) ? x10 : 0))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(85, 17),
                // (108,43): error CS0128: A local variable named 'x14' is already defined in this scope
                //                   TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(108, 43)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyNotAnOutLocal(model, x4Ref[2]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(2, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(3, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_Switch_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        if (true)
            switch (TakeOutParam(1, out var x1) ? 1 : 0)
            {
                case 0:
                    break;
            }

        Dummy(x1, 1);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (19,15): error CS0103: The name 'x1' does not exist in the current context
                //         Dummy(x1, 1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(19, 15)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl);
            VerifyNotInScope(model, x1Ref);
        }

        [Fact]
        public void Scope_Switch_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (SwitchStatementSyntax)SyntaxFactory.ParseStatement(@"
switch (Dummy(TakeOutParam(true, out var x1), x1)) {}
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Switch_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test1(0);
        Test1(1);
    }

    static bool Dummy1(bool val, params object[] x) {return val;}
    static T Dummy2<T>(T val, params object[] x) {return val;}

    static void Test1(int val)
    {
        switch (Dummy2(val, TakeOutParam(""Test1 {0}"", out var x1)))
        {
            case 0 when Dummy1(true, TakeOutParam(""case 0"", out var y1)):
                System.Console.WriteLine(x1, y1);
                break;
            case int z1:
                System.Console.WriteLine(x1, z1);
                break;
        }

        System.Console.WriteLine(x1);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"Test1 case 0
Test1 {0}
Test1 1
Test1 {0}");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Switch_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        if (f)        
            switch (Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1))
            {}

        if (f)        
        {
            switch (Dummy(f, TakeOutParam((f ? 3 : 4), out var x1), x1))
            {}
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void Scope_SwitchLabelGuard_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) { return true; }

    void Test1(int val)
    {
        switch (val)
        {
            case 0 when Dummy(TakeOutParam(true, out var x1), x1):
                Dummy(x1);
                break;
            case 1 when Dummy(TakeOutParam(true, out var x1), x1):
                Dummy(x1);
                break;
            case 2 when Dummy(TakeOutParam(true, out var x1), x1):
                Dummy(x1);
                break;
        }
    }

    void Test2(int val)
    {
        switch (val)
        {
            case 0 when Dummy(x2, TakeOutParam(true, out var x2)):
                Dummy(x2);
                break;
        }
    }

    void Test3(int x3, int val)
    {
        switch (val)
        {
            case 0 when Dummy(TakeOutParam(true, out var x3), x3):
                Dummy(x3);
                break;
        }
    }

    void Test4(int val)
    {
        var x4 = 11;
        switch (val)
        {
            case 0 when Dummy(TakeOutParam(true, out var x4), x4):
                Dummy(x4);
                break;
            case 1 when Dummy(x4): Dummy(x4); break;
        }
    }

    void Test5(int val)
    {
        switch (val)
        {
            case 0 when Dummy(TakeOutParam(true, out var x5), x5):
                Dummy(x5);
                break;
        }
        
        var x5 = 11;
        Dummy(x5);
    }

    //void Test6(int val)
    //{
    //    let x6 = 11;
    //    switch (val)
    //    {
    //        case 0 when Dummy(x6):
    //            Dummy(x6);
    //            break;
    //        case 1 when Dummy(TakeOutParam(true, out var x6), x6):
    //            Dummy(x6);
    //            break;
    //    }
    //}

    //void Test7(int val)
    //{
    //    switch (val)
    //    {
    //        case 0 when Dummy(TakeOutParam(true, out var x7), x7):
    //            Dummy(x7);
    //            break;
    //    }
        
    //    let x7 = 11;
    //    Dummy(x7);
    //}

    void Test8(int val)
    {
        switch (val)
        {
            case 0 when Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8):
                Dummy(x8);
                break;
        }
    }

    void Test9(int val)
    {
        switch (val)
        {
            case 0 when Dummy(x9):
                int x9 = 9;
                Dummy(x9);
                break;
            case 2 when Dummy(x9 = 9):
                Dummy(x9);
                break;
            case 1 when Dummy(TakeOutParam(true, out var x9), x9):
                Dummy(x9);
                break;
        }
    }

    //void Test10(int val)
    //{
    //    switch (val)
    //    {
    //        case 1 when Dummy(TakeOutParam(true, out var x10), x10):
    //            Dummy(x10);
    //            break;
    //        case 0 when Dummy(x10):
    //            let x10 = 10;
    //            Dummy(x10);
    //            break;
    //        case 2 when Dummy(x10 = 10, x10):
    //            Dummy(x10);
    //            break;
    //    }
    //}

    void Test11(int val)
    {
        switch (x11 ? val : 0)
        {
            case 0 when Dummy(x11):
                Dummy(x11, 0);
                break;
            case 1 when Dummy(TakeOutParam(true, out var x11), x11):
                Dummy(x11, 1);
                break;
        }
    }

    void Test12(int val)
    {
        switch (x12 ? val : 0)
        {
            case 0 when Dummy(TakeOutParam(true, out var x12), x12):
                Dummy(x12, 0);
                break;
            case 1 when Dummy(x12):
                Dummy(x12, 1);
                break;
        }
    }

    void Test13()
    {
        switch (TakeOutParam(1, out var x13) ? x13 : 0)
        {
            case 0 when Dummy(x13):
                Dummy(x13);
                break;
            case 1 when Dummy(TakeOutParam(true, out var x13), x13):
                Dummy(x13);
                break;
        }
    }

    void Test14(int val)
    {
        switch (val)
        {
            case 1 when Dummy(TakeOutParam(true, out var x14), x14):
                Dummy(x14);
                Dummy(TakeOutParam(true, out var x14), x14);
                Dummy(x14);
                break;
        }
    }

    void Test15(int val)
    {
        switch (val)
        {
            case 0 when Dummy(TakeOutParam(true, out var x15), x15):
            case 1 when Dummy(TakeOutParam(true, out var x15), x15):
                Dummy(x15);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (30,31): error CS0841: Cannot use local variable 'x2' before it is declared
                //             case 0 when Dummy(x2, TakeOutParam(true, out var x2)):
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x2").WithArguments("x2").WithLocation(30, 31),
                // (40,58): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case 0 when Dummy(TakeOutParam(true, out var x3), x3):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(40, 58),
                // (51,58): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case 0 when Dummy(TakeOutParam(true, out var x4), x4):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(51, 58),
                // (62,58): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case 0 when Dummy(TakeOutParam(true, out var x5), x5):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(62, 58),
                // (102,95): error CS0128: A local variable named 'x8' is already defined in this scope
                //             case 0 when Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8):
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(102, 95),
                // (112,31): error CS0841: Cannot use local variable 'x9' before it is declared
                //             case 0 when Dummy(x9):
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x9").WithArguments("x9").WithLocation(112, 31),
                // (119,58): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case 1 when Dummy(TakeOutParam(true, out var x9), x9):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(119, 58),
                // (144,17): error CS0103: The name 'x11' does not exist in the current context
                //         switch (x11 ? val : 0)
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x11").WithArguments("x11").WithLocation(144, 17),
                // (146,31): error CS0103: The name 'x11' does not exist in the current context
                //             case 0 when Dummy(x11):
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x11").WithArguments("x11").WithLocation(146, 31),
                // (147,23): error CS0103: The name 'x11' does not exist in the current context
                //                 Dummy(x11, 0);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x11").WithArguments("x11").WithLocation(147, 23),
                // (157,17): error CS0103: The name 'x12' does not exist in the current context
                //         switch (x12 ? val : 0)
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x12").WithArguments("x12").WithLocation(157, 17),
                // (162,31): error CS0103: The name 'x12' does not exist in the current context
                //             case 1 when Dummy(x12):
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x12").WithArguments("x12").WithLocation(162, 31),
                // (163,23): error CS0103: The name 'x12' does not exist in the current context
                //                 Dummy(x12, 1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x12").WithArguments("x12").WithLocation(163, 23),
                // (175,58): error CS0136: A local or parameter named 'x13' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case 1 when Dummy(TakeOutParam(true, out var x13), x13):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x13").WithArguments("x13").WithLocation(175, 58),
                // (185,58): error CS0136: A local or parameter named 'x14' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case 1 when Dummy(TakeOutParam(true, out var x14), x14):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x14").WithArguments("x14").WithLocation(185, 58),
                // (198,58): error CS0128: A local variable named 'x15' is already defined in this scope
                //             case 1 when Dummy(TakeOutParam(true, out var x15), x15):
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x15").WithArguments("x15").WithLocation(198, 58),
                // (198,64): error CS0165: Use of unassigned local variable 'x15'
                //             case 1 when Dummy(TakeOutParam(true, out var x15), x15):
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x15").WithArguments("x15").WithLocation(198, 64)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Decl.Length);
            Assert.Equal(6, x1Ref.Length);
            for (int i = 0; i < x1Decl.Length; i++)
            {
                VerifyModelForOutVar(model, x1Decl[i], x1Ref[i * 2], x1Ref[i * 2 + 1]);
            }

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(4, x4Ref.Length);
            VerifyModelForOutVar(model, x4Decl, x4Ref[0], x4Ref[1]);
            VerifyNotAnOutLocal(model, x4Ref[2]);
            VerifyNotAnOutLocal(model, x4Ref[3]);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(3, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl, x5Ref[0], x5Ref[1]);
            VerifyNotAnOutLocal(model, x5Ref[2]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Decl.Length);
            Assert.Equal(3, x8Ref.Length);
            for (int i = 0; i < x8Ref.Length; i++)
            {
                VerifyModelForOutVar(model, x8Decl[0], x8Ref[i]);
            }
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl[1]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(6, x9Ref.Length);
            VerifyNotAnOutLocal(model, x9Ref[0]);
            VerifyNotAnOutLocal(model, x9Ref[1]);
            VerifyNotAnOutLocal(model, x9Ref[2]);
            VerifyNotAnOutLocal(model, x9Ref[3]);
            VerifyModelForOutVar(model, x9Decl, x9Ref[4], x9Ref[5]);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(5, x11Ref.Length);
            VerifyNotInScope(model, x11Ref[0]);
            VerifyNotInScope(model, x11Ref[1]);
            VerifyNotInScope(model, x11Ref[2]);
            VerifyModelForOutVar(model, x11Decl, x11Ref[3], x11Ref[4]);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(5, x12Ref.Length);
            VerifyNotInScope(model, x12Ref[0]);
            VerifyModelForOutVar(model, x12Decl, x12Ref[1], x12Ref[2]);
            VerifyNotInScope(model, x12Ref[3]);
            VerifyNotInScope(model, x12Ref[4]);

            var x13Decl = GetOutVarDeclarations(tree, "x13").ToArray();
            var x13Ref = GetReferences(tree, "x13").ToArray();
            Assert.Equal(2, x13Decl.Length);
            Assert.Equal(5, x13Ref.Length);
            VerifyModelForOutVar(model, x13Decl[0], x13Ref[0], x13Ref[1], x13Ref[2]);
            VerifyModelForOutVar(model, x13Decl[1], x13Ref[3], x13Ref[4]);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(4, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVar(model, x14Decl[1], isDelegateCreation: false, isExecutableCode: true, isShadowed: true);

            var x15Decl = GetOutVarDeclarations(tree, "x15").ToArray();
            var x15Ref = GetReferences(tree, "x15").ToArray();
            Assert.Equal(2, x15Decl.Length);
            Assert.Equal(3, x15Ref.Length);
            for (int i = 0; i < x15Ref.Length; i++)
            {
                VerifyModelForOutVar(model, x15Decl[0], x15Ref[i]);
            }
            VerifyModelForOutVarDuplicateInSameScope(model, x15Decl[1]);
        }

        [Fact]
        public void Scope_SwitchLabelGuard_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                TakeOutParam(x1, out var y1);
                System.Console.WriteLine(y1);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                while (TakeOutParam(x1, out var y1) && Print(y1)) break;
                break;
        }
    }

    static bool Print(int x)
    {
        System.Console.WriteLine(x);
        return false;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                do
                    val = 0;
                while (TakeOutParam(x1, out var y1) && Print(y1));
                break;
        }
    }

    static bool Print(int x)
    {
        System.Console.WriteLine(x);
        return false;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                lock ((object)TakeOutParam(x1, out var y1)) {}
                System.Console.WriteLine(y1);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                if (TakeOutParam(x1, out var y1)) {}
                System.Console.WriteLine(y1);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_07()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                switch (TakeOutParam(x1, out var y1)) 
                {
                    default: break;
                }
                System.Console.WriteLine(y1);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_08()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        foreach (var x in Test(1)) {}
    }

    static System.Collections.IEnumerable Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                yield return TakeOutParam(x1, out var y1);
                System.Console.WriteLine(y1);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_09()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                var z1 = x1 > 0 & TakeOutParam(x1, out var y1);
                System.Console.WriteLine(y1);
                System.Console.WriteLine(z1 ? 1 : 0);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"123
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");
            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());

            model = compilation.GetSemanticModel(tree);
            var zRef = GetReference(tree, "z1");
            Assert.Equal("System.Boolean", model.GetTypeInfo(zRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_10()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
a:              TakeOutParam(x1, out var y1);
                System.Console.WriteLine(y1);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics(
                // (14,1): warning CS0164: This label has not been referenced
                // a:              TakeOutParam(x1, out var y1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(14, 1)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_11()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static bool Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                return TakeOutParam(x1, out var y1) && Print(y1);
                System.Console.WriteLine(y1);
                break;
        }

        return false;
    }

    static bool Print<T>(T x)
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics(
                // (15,17): warning CS0162: Unreachable code detected
                //                 System.Console.WriteLine(y1);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "System").WithLocation(15, 17)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReferences(tree, "y1").Last();

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelGuard_12()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static bool Test(int val)
    {
        try
        {
            switch (val)
            {
                case 1 when TakeOutParam(123, out var x1):
                    throw Dummy(TakeOutParam(x1, out var y1), y1);
                    System.Console.WriteLine(y1);
                    break;
            }
        }
        catch 
        {}

        return false;
    }

    static System.Exception Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new System.ArgumentException();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics(
                // (17,21): warning CS0162: Unreachable code detected
                //                     System.Console.WriteLine(y1);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "System").WithLocation(17, 21)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReferences(tree, "y1").Last();

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_SwitchLabelGuard_13()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                var (z0, z1)  = (x1 > 0, TakeOutParam(x1, out var y1));
                System.Console.WriteLine(y1);
                System.Console.WriteLine(z1 ? 1 : 0);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"123
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");
            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());

            model = compilation.GetSemanticModel(tree);
            var zRef = GetReference(tree, "z1");
            Assert.Equal("System.Boolean", model.GetTypeInfo(zRef).Type.ToTestDisplayString());
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void Scope_SwitchLabelGuard_14()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                var (z0, (z1, z2))  = (x1 > 0, (TakeOutParam(x1, out var y1), true));
                System.Console.WriteLine(y1);
                System.Console.WriteLine(z1 ? 1 : 0);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"123
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y1");
            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());

            model = compilation.GetSemanticModel(tree);
            var zRef = GetReference(tree, "z1");
            Assert.Equal("System.Boolean", model.GetTypeInfo(zRef).Type.ToTestDisplayString());
        }

        [Fact]
        public void Scope_SwitchLabelPattern_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) { return true; }

    void Test8(object val)
    {
        switch (val)
        {
            case int x8 
                    when Dummy(x8, TakeOutParam(false, out var x8), x8):
                Dummy(x8);
                break;
        }
    }

    void Test13()
    {
        switch (TakeOutParam(1, out var x13) ? x13 : 0)
        {
            case 0 when Dummy(x13):
                Dummy(x13);
                break;
            case int x13 when Dummy(x13):
                Dummy(x13);
                break;
        }
    }

    void Test14(object val)
    {
        switch (val)
        {
            case int x14 when Dummy(x14):
                Dummy(x14);
                Dummy(TakeOutParam(true, out var x14), x14);
                Dummy(x14);
                break;
        }
    }

    void Test16(object val)
    {
        switch (val)
        {
            case int x16 when Dummy(x16):
            case 1 when Dummy(TakeOutParam(true, out var x16), x16):
                Dummy(x16);
                break;
        }
    }

    void Test17(object val)
    {
        switch (val)
        {
            case 0 when Dummy(TakeOutParam(true, out var x17), x17):
            case int x17 when Dummy(x17):
                Dummy(x17);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (15,64): error CS0128: A local variable named 'x8' is already defined in this scope
                //                     when Dummy(x8, TakeOutParam(false, out var x8), x8):
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(15, 64),
                // (28,22): error CS0136: A local or parameter named 'x13' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case int x13 when Dummy(x13):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x13").WithArguments("x13").WithLocation(28, 22),
                // (38,22): error CS0136: A local or parameter named 'x14' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             case int x14 when Dummy(x14):
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x14").WithArguments("x14").WithLocation(38, 22),
                // (51,58): error CS0128: A local variable named 'x16' is already defined in this scope
                //             case 1 when Dummy(TakeOutParam(true, out var x16), x16):
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x16").WithArguments("x16").WithLocation(51, 58),
                // (51,64): error CS0165: Use of unassigned local variable 'x16'
                //             case 1 when Dummy(TakeOutParam(true, out var x16), x16):
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x16").WithArguments("x16").WithLocation(51, 64),
                // (62,22): error CS0128: A local variable named 'x17' is already defined in this scope
                //             case int x17 when Dummy(x17):
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x17").WithArguments("x17").WithLocation(62, 22),
                // (62,37): error CS0165: Use of unassigned local variable 'x17'
                //             case int x17 when Dummy(x17):
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x17").WithArguments("x17").WithLocation(62, 37)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            for (int i = 0; i < x8Ref.Length; i++)
            {
                VerifyNotAnOutLocal(model, x8Ref[i]);
            }
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl);

            var x13Decl = GetOutVarDeclarations(tree, "x13").Single();
            var x13Ref = GetReferences(tree, "x13").ToArray();
            Assert.Equal(5, x13Ref.Length);
            VerifyModelForOutVar(model, x13Decl, x13Ref[0], x13Ref[1], x13Ref[2]);
            VerifyNotAnOutLocal(model, x13Ref[3]);
            VerifyNotAnOutLocal(model, x13Ref[4]);

            var x14Decl = GetOutVarDeclarations(tree, "x14").Single();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(4, x14Ref.Length);
            VerifyNotAnOutLocal(model, x14Ref[0]);
            VerifyNotAnOutLocal(model, x14Ref[1]);
            VerifyNotAnOutLocal(model, x14Ref[2]);
            VerifyNotAnOutLocal(model, x14Ref[3]);
            VerifyModelForOutVar(model, x14Decl, isDelegateCreation: false, isExecutableCode: true, isShadowed: true);

            var x16Decl = GetOutVarDeclarations(tree, "x16").Single();
            var x16Ref = GetReferences(tree, "x16").ToArray();
            Assert.Equal(3, x16Ref.Length);
            for (int i = 0; i < x16Ref.Length; i++)
            {
                VerifyNotAnOutLocal(model, x16Ref[i]);
            }
            VerifyModelForOutVarDuplicateInSameScope(model, x16Decl);

            var x17Decl = GetOutVarDeclarations(tree, "x17").Single();
            var x17Ref = GetReferences(tree, "x17").ToArray();
            Assert.Equal(3, x17Ref.Length);
            VerifyModelForOutVar(model, x17Decl, x17Ref);
        }

        [Fact]
        public void Scope_ThrowStatement_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.Exception Dummy(params object[] x) { return null;}

    void Test1()
    {
        throw Dummy(TakeOutParam(true, out var x1), x1);
        {
            throw Dummy(TakeOutParam(true, out var x1), x1);
        }
        throw Dummy(TakeOutParam(true, out var x1), x1);
    }

    void Test2()
    {
        throw Dummy(x2, TakeOutParam(true, out var x2));
    }

    void Test3(int x3)
    {
        throw Dummy(TakeOutParam(true, out var x3), x3);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);
        throw Dummy(TakeOutParam(true, out var x4), x4);
    }

    void Test5()
    {
        throw Dummy(TakeOutParam(true, out var x5), x5);
        var x5 = 11;
        Dummy(x5);
    }

    //void Test6()
    //{
    //    let x6 = 11;
    //    Dummy(x6);
    //    throw Dummy(TakeOutParam(true, out var x6), x6);
    //}

    //void Test7()
    //{
    //    throw Dummy(TakeOutParam(true, out var x7), x7);
    //    let x7 = 11;
    //    Dummy(x7);
    //}

    void Test8()
    {
        throw Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
    }

    void Test9(bool y9)
    {
        if (y9)
            throw Dummy(TakeOutParam(true, out var x9), x9);
    }

    System.Action Test10(bool y10)
    {
        return () =>
                {
                    if (y10)
                        throw Dummy(TakeOutParam(true, out var x10), x10);
                };
    }

    void Test11()
    {
        Dummy(x11);
        throw Dummy(TakeOutParam(true, out var x11), x11);
    }

    void Test12()
    {
        throw Dummy(TakeOutParam(true, out var x12), x12);
        Dummy(x12);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (14,52): error CS0136: A local or parameter named 'x1' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             throw Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x1").WithArguments("x1").WithLocation(14, 52),
                // (16,48): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //         throw Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(16, 48),
                // (21,21): error CS0841: Cannot use local variable 'x2' before it is declared
                //         throw Dummy(x2, TakeOutParam(true, out var x2));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x2").WithArguments("x2").WithLocation(21, 21),
                // (26,48): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         throw Dummy(TakeOutParam(true, out var x3), x3);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(26, 48),
                // (33,48): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //         throw Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(33, 48),
                // (39,13): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //         var x5 = 11;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(39, 13),
                // (39,9): warning CS0162: Unreachable code detected
                //         var x5 = 11;
                Diagnostic(ErrorCode.WRN_UnreachableCode, "var").WithLocation(39, 9),
                // (39,13): warning CS0219: The variable 'x5' is assigned but its value is never used
                //         var x5 = 11;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x5").WithArguments("x5").WithLocation(39, 13),
                // (59,85): error CS0128: A local variable or function named 'x8' is already defined in this scope
                //         throw Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(59, 85),
                // (79,15): error CS0841: Cannot use local variable 'x11' before it is declared
                //         Dummy(x11);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x11").WithArguments("x11").WithLocation(79, 15),
                // (86,9): warning CS0162: Unreachable code detected
                //         Dummy(x12);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "Dummy").WithLocation(86, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl[2]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(2, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Decl.Length);
            Assert.Equal(2, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl[0], x8Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl[1]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReferences(tree, "x9").Single();
            VerifyModelForOutVar(model, x9Decl, x9Ref);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            VerifyModelForOutVar(model, x10Decl, x10Ref);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(2, x11Ref.Length);
            VerifyModelForOutVar(model, x11Decl, x11Ref);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(2, x12Ref.Length);
            VerifyModelForOutVar(model, x12Decl, x12Ref);
        }

        [Fact]
        public void Scope_ThrowStatement_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.Exception Dummy(params object[] x) { return null;}

    void Test1(bool val)
    {
        if (val)
            throw Dummy(TakeOutParam(true, out var x1));

        x1++;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (15,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(15, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0]);
            VerifyNotInScope(model, x1Ref[0]);
        }

        [Fact]
        public void Scope_ThrowStatement_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (ThrowStatementSyntax)SyntaxFactory.ParseStatement(@"
throw Dummy(TakeOutParam(true, out var x1), x1);
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Throw_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test();
    }

    static void Test()
    {
        try
        {
            throw Dummy(TakeOutParam(""throw"", out var x2), x2);
        }
        catch
        {
        }
    }

    static System.Exception Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new System.ArgumentException();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"throw");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(1, x2Decl.Length);
            Assert.Equal(1, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref);
        }

        [Fact]
        public void Throw_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(true);
        Test(false);
    }

    static void Test(bool val)
    {
        try
        {
            if (val)
                throw Dummy(TakeOutParam(""throw 1"", out var x2), x2);

            if (!val)
            {
                throw Dummy(TakeOutParam(""throw 2"", out var x2), x2);
            }
        }
        catch
        {
        }
    }

    static System.Exception Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new System.ArgumentException();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"throw 1
throw 2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref[0]);
            VerifyModelForOutVar(model, x2Decl[1], x2Ref[1]);
        }

        [Fact]
        public void Scope_Using_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (Dummy(TakeOutParam(true, out var x1), x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (Dummy(TakeOutParam(true, out var x2), x2))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        using (Dummy(TakeOutParam(true, out var x4), x4))
            Dummy(x4);
    }

    void Test6()
    {
        using (Dummy(x6 && TakeOutParam(true, out var x6)))
            Dummy(x6);
    }

    void Test7()
    {
        using (Dummy(TakeOutParam(true, out var x7) && x7))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        using (Dummy(TakeOutParam(true, out var x8), x8))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        using (Dummy(TakeOutParam(true, out var x9), x9))
        {   
            Dummy(x9);
            using (Dummy(TakeOutParam(true, out var x9), x9)) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        using (Dummy(TakeOutParam(y10, out var x10), x10))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    using (Dummy(TakeOutParam(y11, out var x11), x11))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        using (Dummy(TakeOutParam(y12, out var x12), x12))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    using (Dummy(TakeOutParam(y13, out var x13), x13))
    //        let y13 = 12;
    //}

    void Test14()
    {
        using (Dummy(TakeOutParam(1, out var x14), 
                     TakeOutParam(2, out var x14), 
                     x14))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,49): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         using (Dummy(TakeOutParam(true, out var x4), x4))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 49),
                // (35,22): error CS0841: Cannot use local variable 'x6' before it is declared
                //         using (Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 22),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,53): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             using (Dummy(TakeOutParam(true, out var x9), x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 53),
                // (68,35): error CS0103: The name 'y10' does not exist in the current context
                //         using (Dummy(TakeOutParam(y10, out var x10), x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 35),
                // (86,35): error CS0103: The name 'y12' does not exist in the current context
                //         using (Dummy(TakeOutParam(y12, out var x12), x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 35),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,46): error CS0128: A local variable named 'x14' is already defined in this scope
                //                      TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 46)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            VerifyModelForOutVar(model, x10Decl, x10Ref);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_Using_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (var d = Dummy(TakeOutParam(true, out var x1), x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (var d = Dummy(TakeOutParam(true, out var x2), x2))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        using (var d = Dummy(TakeOutParam(true, out var x4), x4))
            Dummy(x4);
    }

    void Test6()
    {
        using (var d = Dummy(x6 && TakeOutParam(true, out var x6)))
            Dummy(x6);
    }

    void Test7()
    {
        using (var d = Dummy(TakeOutParam(true, out var x7) && x7))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        using (var d = Dummy(TakeOutParam(true, out var x8), x8))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        using (var d = Dummy(TakeOutParam(true, out var x9), x9))
        {   
            Dummy(x9);
            using (var e = Dummy(TakeOutParam(true, out var x9), x9)) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        using (var d = Dummy(TakeOutParam(y10, out var x10), x10))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    using (var d = Dummy(TakeOutParam(y11, out var x11), x11))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        using (var d = Dummy(TakeOutParam(y12, out var x12), x12))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    using (var d = Dummy(TakeOutParam(y13, out var x13), x13))
    //        let y13 = 12;
    //}

    void Test14()
    {
        using (var d = Dummy(TakeOutParam(1, out var x14), 
                             TakeOutParam(2, out var x14), 
                             x14))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,57): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         using (var d = Dummy(TakeOutParam(true, out var x4), x4))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 57),
                // (35,30): error CS0841: Cannot use local variable 'x6' before it is declared
                //         using (var d = Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 30),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,61): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             using (var e = Dummy(TakeOutParam(true, out var x9), x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 61),
                // (68,43): error CS0103: The name 'y10' does not exist in the current context
                //         using (var d = Dummy(TakeOutParam(y10, out var x10), x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 43),
                // (86,43): error CS0103: The name 'y12' does not exist in the current context
                //         using (var d = Dummy(TakeOutParam(y12, out var x12), x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 43),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,54): error CS0128: A local variable named 'x14' is already defined in this scope
                //                              TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 54)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            VerifyModelForOutVar(model, x10Decl, x10Ref);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_Using_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(true, out var x1), x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(true, out var x2), x2))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        using (System.IDisposable d = Dummy(TakeOutParam(true, out var x4), x4))
            Dummy(x4);
    }

    void Test6()
    {
        using (System.IDisposable d = Dummy(x6 && TakeOutParam(true, out var x6)))
            Dummy(x6);
    }

    void Test7()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(true, out var x7) && x7))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(true, out var x8), x8))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(true, out var x9), x9))
        {   
            Dummy(x9);
            using (System.IDisposable c = Dummy(TakeOutParam(true, out var x9), x9)) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(y10, out var x10), x10))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    using (System.IDisposable d = Dummy(TakeOutParam(y11, out var x11), x11))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(y12, out var x12), x12))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    using (System.IDisposable d = Dummy(TakeOutParam(y13, out var x13), x13))
    //        let y13 = 12;
    //}

    void Test14()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(1, out var x14), 
                                            TakeOutParam(2, out var x14), 
                                            x14))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,72): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         using (System.IDisposable d = Dummy(TakeOutParam(true, out var x4), x4))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 72),
                // (35,45): error CS0841: Cannot use local variable 'x6' before it is declared
                //         using (System.IDisposable d = Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 45),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,76): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             using (System.IDisposable c = Dummy(TakeOutParam(true, out var x9), x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 76),
                // (68,58): error CS0103: The name 'y10' does not exist in the current context
                //         using (System.IDisposable d = Dummy(TakeOutParam(y10, out var x10), x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 58),
                // (86,58): error CS0103: The name 'y12' does not exist in the current context
                //         using (System.IDisposable d = Dummy(TakeOutParam(y12, out var x12), x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 58),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,69): error CS0128: A local variable named 'x14' is already defined in this scope
                //                                             TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 69)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            VerifyModelForOutVar(model, x10Decl, x10Ref);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_Using_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (var x1 = Dummy(TakeOutParam(true, out var x1), x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (System.IDisposable x2 = Dummy(TakeOutParam(true, out var x2), x2))
        {
            Dummy(x2);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (12,58): error CS0128: A local variable named 'x1' is already defined in this scope
                //         using (var x1 = Dummy(TakeOutParam(true, out var x1), x1))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(12, 58),
                // (12,63): error CS0841: Cannot use local variable 'x1' before it is declared
                //         using (var x1 = Dummy(TakeOutParam(true, out var x1), x1))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x1").WithArguments("x1").WithLocation(12, 63),
                // (20,73): error CS0128: A local variable named 'x2' is already defined in this scope
                //         using (System.IDisposable x2 = Dummy(TakeOutParam(true, out var x2), x2))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 73),
                // (20,78): error CS0165: Use of unassigned local variable 'x2'
                //         using (System.IDisposable x2 = Dummy(TakeOutParam(true, out var x2), x2))
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(20, 78)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
            VerifyNotAnOutLocal(model, x2Ref[0]);
            VerifyNotAnOutLocal(model, x2Ref[1]);
        }

        [Fact]
        public void Scope_Using_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (System.IDisposable d = Dummy(TakeOutParam(true, out var x1), x1), 
                                  x1 = Dummy(x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (System.IDisposable d1 = Dummy(TakeOutParam(true, out var x2), x2), 
                                  d2 = Dummy(TakeOutParam(true, out var x2), x2))
        {
            Dummy(x2);
        }
    }

    void Test3()
    {
        using (System.IDisposable d1 = Dummy(TakeOutParam(true, out var x3), x3), 
                                  d2 = Dummy(x3))
        {
            Dummy(x3);
        }
    }

    void Test4()
    {
        using (System.IDisposable d1 = Dummy(x4), 
                                  d2 = Dummy(TakeOutParam(true, out var x4), x4))
        {
            Dummy(x4);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (13,35): error CS0128: A local variable named 'x1' is already defined in this scope
                //                                   x1 = Dummy(x1))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 35),
                // (22,73): error CS0128: A local variable named 'x2' is already defined in this scope
                //                                   d2 = Dummy(TakeOutParam(true, out var x2), x2))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(22, 73),
                // (39,46): error CS0841: Cannot use local variable 'x4' before it is declared
                //         using (System.IDisposable d1 = Dummy(x4), 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(39, 46)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(3, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl[1]);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(3, x3Ref.Length);
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyModelForOutVar(model, x4Decl, x4Ref);
        }

        [Fact]
        public void Using_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        using (System.IDisposable d1 = Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1)),
                                  d2 = Dummy(new C(""c""), TakeOutParam(new C(""d""), out var x2)))
        {
            System.Console.WriteLine(d1);
            System.Console.WriteLine(x1);
            System.Console.WriteLine(d2);
            System.Console.WriteLine(x2);
        }

        using (Dummy(new C(""e""), TakeOutParam(new C(""f""), out var x1)))
        {
            System.Console.WriteLine(x1);
        }
    }

    static System.IDisposable Dummy(System.IDisposable x, params object[] y) {return x;}

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}

class C : System.IDisposable
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public void Dispose()
    {
        System.Console.WriteLine(""Disposing {0}"", _val);
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"a
b
c
d
Disposing c
Disposing a
f
Disposing e");
        }

        [Fact]
        public void Scope_While_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        while (TakeOutParam(true, out var x1) && x1)
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        while (TakeOutParam(true, out var x2) && x2)
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        while (TakeOutParam(true, out var x4) && x4)
            Dummy(x4);
    }

    void Test6()
    {
        while (x6 && TakeOutParam(true, out var x6))
            Dummy(x6);
    }

    void Test7()
    {
        while (TakeOutParam(true, out var x7) && x7)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        while (TakeOutParam(true, out var x8) && x8)
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        while (TakeOutParam(true, out var x9) && x9)
        {   
            Dummy(x9);
            while (TakeOutParam(true, out var x9) && x9) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        while (TakeOutParam(y10, out var x10))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    while (TakeOutParam(y11, out var x11))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        while (TakeOutParam(y12, out var x12))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    while (TakeOutParam(y13, out var x13))
    //        let y13 = 12;
    //}

    void Test14()
    {
        while (Dummy(TakeOutParam(1, out var x14), 
                     TakeOutParam(2, out var x14), 
                     x14))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,43): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         while (TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 43),
                // (35,16): error CS0841: Cannot use local variable 'x6' before it is declared
                //         while (x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 16),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,47): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             while (TakeOutParam(true, out var x9) && x9) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 47),
                // (68,29): error CS0103: The name 'y10' does not exist in the current context
                //         while (TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 29),
                // (86,29): error CS0103: The name 'y12' does not exist in the current context
                //         while (TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 29),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,46): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                      TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 46)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            VerifyModelForOutVar(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_While_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        if (true)
            while (TakeOutParam(true, out var x1))
            {
                ;
            }

        x1++;
    }
    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (18,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(18, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl);
            VerifyNotInScope(model, x1Ref);
        }

        [Fact]
        public void Scope_While_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (WhileStatementSyntax)SyntaxFactory.ParseStatement(@"
while (Dummy(TakeOutParam(true, out var x1), x1));
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void While_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        while (Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1))
        {
            System.Console.WriteLine(x1);
            f = false;
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
1
2
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void While_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        bool f = true;

        if (f)        
            while (Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1))
                f = false;

        f = true;

        if (f)        
        {
            while (Dummy(f, TakeOutParam((f ? 3 : 4), out var x1), x1))
                f = false;
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
2
3
4");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void While_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        int f = 1;
        var l = new System.Collections.Generic.List<System.Action>();

        while (Dummy(f < 3, TakeOutParam(f, out var x1), x1))
        {
            l.Add(() => System.Console.WriteLine(x1));
            f++;
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static bool Dummy(bool x, object y, object z) 
    {
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
2
3
--
1
2
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void While_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        int f = 1;
        var l = new System.Collections.Generic.List<System.Action>();

        while (Dummy(f < 3, TakeOutParam(f, out var x1), x1, l, () => System.Console.WriteLine(x1)))
        {
            f++;
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static bool Dummy(bool x, object y, object z, System.Collections.Generic.List<System.Action> l, System.Action d) 
    {
        l.Add(d);
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
2
3
--
1
2
3
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void While_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        int f = 1;
        var l = new System.Collections.Generic.List<System.Action>();

        while (Dummy(f < 3, TakeOutParam(f, out var x1), x1, l, () => System.Console.WriteLine(x1)))
        {
            l.Add(() => System.Console.WriteLine(x1));
            f++;
        }

        System.Console.WriteLine(""--"");

        foreach (var d in l)
        {
            d();
        }
    }

    static bool Dummy(bool x, object y, object z, System.Collections.Generic.List<System.Action> l, System.Action d) 
    {
        l.Add(d);
        System.Console.WriteLine(z);
        return x;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"1
2
3
--
1
1
2
2
3
");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Scope_Yield_01()
        {
            var source =
@"
using System.Collections;

public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) { return null;}

    IEnumerable Test1()
    {
        yield return Dummy(TakeOutParam(true, out var x1), x1);
        {
            yield return Dummy(TakeOutParam(true, out var x1), x1);
        }
        yield return Dummy(TakeOutParam(true, out var x1), x1);
    }

    IEnumerable Test2()
    {
        yield return Dummy(x2, TakeOutParam(true, out var x2));
    }

    IEnumerable Test3(int x3)
    {
        yield return Dummy(TakeOutParam(true, out var x3), x3);
    }

    IEnumerable Test4()
    {
        var x4 = 11;
        Dummy(x4);
        yield return Dummy(TakeOutParam(true, out var x4), x4);
    }

    IEnumerable Test5()
    {
        yield return Dummy(TakeOutParam(true, out var x5), x5);
        var x5 = 11;
        Dummy(x5);
    }

    //IEnumerable Test6()
    //{
    //    let x6 = 11;
    //    Dummy(x6);
    //    yield return Dummy(TakeOutParam(true, out var x6), x6);
    //}

    //IEnumerable Test7()
    //{
    //    yield return Dummy(TakeOutParam(true, out var x7), x7);
    //    let x7 = 11;
    //    Dummy(x7);
    //}

    IEnumerable Test8()
    {
        yield return Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
    }

    IEnumerable Test9(bool y9)
    {
        if (y9)
            yield return Dummy(TakeOutParam(true, out var x9), x9);
    }

    IEnumerable Test11()
    {
        Dummy(x11);
        yield return Dummy(TakeOutParam(true, out var x11), x11);
    }

    IEnumerable Test12()
    {
        yield return Dummy(TakeOutParam(true, out var x12), x12);
        Dummy(x12);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (16,59): error CS0136: A local or parameter named 'x1' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             yield return Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x1").WithArguments("x1").WithLocation(16, 59),
                // (18,55): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //         yield return Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(18, 55),
                // (23,28): error CS0841: Cannot use local variable 'x2' before it is declared
                //         yield return Dummy(x2, TakeOutParam(true, out var x2));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x2").WithArguments("x2").WithLocation(23, 28),
                // (28,55): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         yield return Dummy(TakeOutParam(true, out var x3), x3);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(28, 55),
                // (35,55): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //         yield return Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(35, 55),
                // (41,13): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //         var x5 = 11;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(41, 13),
                // (41,13): warning CS0219: The variable 'x5' is assigned but its value is never used
                //         var x5 = 11;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x5").WithArguments("x5").WithLocation(41, 13),
                // (61,92): error CS0128: A local variable or function named 'x8' is already defined in this scope
                //         yield return Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(61, 92),
                // (72,15): error CS0841: Cannot use local variable 'x11' before it is declared
                //         Dummy(x11);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x11").WithArguments("x11").WithLocation(72, 15)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl[2]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(2, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Decl.Length);
            Assert.Equal(2, x8Ref.Length);
            for (int i = 0; i < x8Decl.Length; i++)
            {
                VerifyModelForOutVar(model, x8Decl[0], x8Ref[i]);
            }
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl[1]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReferences(tree, "x9").Single();
            VerifyModelForOutVar(model, x9Decl, x9Ref);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(2, x11Ref.Length);
            VerifyModelForOutVar(model, x11Decl, x11Ref);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(2, x12Ref.Length);
            VerifyModelForOutVar(model, x12Decl, x12Ref);
        }

        [Fact]
        public void Scope_Yield_02()
        {
            var source =
@"
using System.Collections;

public class X
{
    public static void Main()
    {
    }

    IEnumerable Test1()
    {
        if (true)
            yield return TakeOutParam(true, out var x1);

        x1++;
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (15,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(15, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl);
            VerifyNotInScope(model, x1Ref);
        }

        [Fact]
        public void Scope_Yield_03()
        {
            var source =
@"
using System.Collections;

public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    IEnumerable Test1()
    {
        yield return 0;
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (YieldStatementSyntax)SyntaxFactory.ParseStatement(@"
yield return Dummy(TakeOutParam(true, out var x1), x1);
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Yield_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        foreach (var o in Test())
        {}
    }

    static System.Collections.IEnumerable Test()
    {
        yield return Dummy(TakeOutParam(""yield1"", out var x1), x1);
        yield return Dummy(TakeOutParam(""yield2"", out var x2), x2);
        System.Console.WriteLine(x1);
    }

    static object Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new object();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"yield1
yield2
yield1");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Yield_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        foreach (var o in Test())
        {}
    }

    static System.Collections.IEnumerable Test()
    {
        bool f = true;

        if (f)        
            yield return Dummy(TakeOutParam(""yield1"", out var x1), x1);

        if (f)        
        {
            yield return Dummy(TakeOutParam(""yield2"", out var x1), x1);
        }
    }

    static object Dummy(object y, object z) 
    {
        System.Console.WriteLine(z);
        return new object();
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"yield1
yield2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void Scope_LabeledStatement_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
a:      Dummy(TakeOutParam(true, out var x1), x1);
        {
b:          Dummy(TakeOutParam(true, out var x1), x1);
        }
c:      Dummy(TakeOutParam(true, out var x1), x1);
    }

    void Test2()
    {
a:      Dummy(x2, TakeOutParam(true, out var x2));
    }

    void Test3(int x3)
    {
a:      Dummy(TakeOutParam(true, out var x3), x3);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);
a:      Dummy(TakeOutParam(true, out var x4), x4);
    }

    void Test5()
    {
a:      Dummy(TakeOutParam(true, out var x5), x5);
        var x5 = 11;
        Dummy(x5);
    }

    //void Test6()
    //{
    //    let x6 = 11;
    //    Dummy(x6);
    //a:  Dummy(TakeOutParam(true, out var x6), x6);
    //}

    //void Test7()
    //{
    //a:  Dummy(TakeOutParam(true, out var x7), x7);
    //    let x7 = 11;
    //    Dummy(x7);
    //}

    void Test8()
    {
a:      Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
    }

    void Test9(bool y9)
    {
        if (y9)
a:          Dummy(TakeOutParam(true, out var x9), x9);
    }

    System.Action Test10(bool y10)
    {
        return () =>
                {
                    if (y10)
a:                      Dummy(TakeOutParam(true, out var x10), x10);
                };
    }

    void Test11()
    {
        Dummy(x11);
a:      Dummy(TakeOutParam(true, out var x11), x11);
    }

    void Test12()
    {
a:      Dummy(TakeOutParam(true, out var x12), x12);
        Dummy(x12);
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (14,46): error CS0136: A local or parameter named 'x1' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                // b:          Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x1").WithArguments("x1").WithLocation(14, 46),
                // (16,42): error CS0128: A local variable or function named 'x1' is already defined in this scope
                // c:      Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(16, 42),
                // (12,1): warning CS0164: This label has not been referenced
                // a:      Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(12, 1),
                // (14,1): warning CS0164: This label has not been referenced
                // b:          Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(14, 1),
                // (16,1): warning CS0164: This label has not been referenced
                // c:      Dummy(TakeOutParam(true, out var x1), x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(16, 1),
                // (21,15): error CS0841: Cannot use local variable 'x2' before it is declared
                // a:      Dummy(x2, TakeOutParam(true, out var x2));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x2").WithArguments("x2").WithLocation(21, 15),
                // (21,1): warning CS0164: This label has not been referenced
                // a:      Dummy(x2, TakeOutParam(true, out var x2));
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(21, 1),
                // (26,42): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                // a:      Dummy(TakeOutParam(true, out var x3), x3);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(26, 42),
                // (26,1): warning CS0164: This label has not been referenced
                // a:      Dummy(TakeOutParam(true, out var x3), x3);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(26, 1),
                // (33,42): error CS0128: A local variable or function named 'x4' is already defined in this scope
                // a:      Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(33, 42),
                // (33,1): warning CS0164: This label has not been referenced
                // a:      Dummy(TakeOutParam(true, out var x4), x4);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(33, 1),
                // (39,13): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //         var x5 = 11;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(39, 13),
                // (38,1): warning CS0164: This label has not been referenced
                // a:      Dummy(TakeOutParam(true, out var x5), x5);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(38, 1),
                // (39,13): warning CS0219: The variable 'x5' is assigned but its value is never used
                //         var x5 = 11;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x5").WithArguments("x5").WithLocation(39, 13),
                // (59,79): error CS0128: A local variable or function named 'x8' is already defined in this scope
                // a:      Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(59, 79),
                // (59,1): warning CS0164: This label has not been referenced
                // a:      Dummy(TakeOutParam(true, out var x8), x8, TakeOutParam(false, out var x8), x8);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(59, 1),
                // (65,1): error CS1023: Embedded statement cannot be a declaration or labeled statement
                // a:          Dummy(TakeOutParam(true, out var x9), x9);
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "a:          Dummy(TakeOutParam(true, out var x9), x9);").WithLocation(65, 1),
                // (65,1): warning CS0164: This label has not been referenced
                // a:          Dummy(TakeOutParam(true, out var x9), x9);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(65, 1),
                // (73,1): error CS1023: Embedded statement cannot be a declaration or labeled statement
                // a:                      Dummy(TakeOutParam(true, out var x10), x10);
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "a:                      Dummy(TakeOutParam(true, out var x10), x10);").WithLocation(73, 1),
                // (73,1): warning CS0164: This label has not been referenced
                // a:                      Dummy(TakeOutParam(true, out var x10), x10);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(73, 1),
                // (79,15): error CS0841: Cannot use local variable 'x11' before it is declared
                //         Dummy(x11);
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x11").WithArguments("x11").WithLocation(79, 15),
                // (80,1): warning CS0164: This label has not been referenced
                // a:      Dummy(TakeOutParam(true, out var x11), x11);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(80, 1),
                // (85,1): warning CS0164: This label has not been referenced
                // a:      Dummy(TakeOutParam(true, out var x12), x12);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(85, 1)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl[2]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutVar(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            VerifyModelForOutVar(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
            var x5Ref = GetReferences(tree, "x5").ToArray();
            Assert.Equal(2, x5Ref.Length);
            VerifyModelForOutVar(model, x5Decl, x5Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Decl.Length);
            Assert.Equal(2, x8Ref.Length);
            for (int i = 0; i < x8Decl.Length; i++)
            {
                VerifyModelForOutVar(model, x8Decl[0], x8Ref[i]);
            }
            VerifyModelForOutVarDuplicateInSameScope(model, x8Decl[1]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").Single();
            var x9Ref = GetReferences(tree, "x9").Single();
            VerifyModelForOutVar(model, x9Decl, x9Ref);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            VerifyModelForOutVar(model, x10Decl, x10Ref);

            var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
            var x11Ref = GetReferences(tree, "x11").ToArray();
            Assert.Equal(2, x11Ref.Length);
            VerifyModelForOutVar(model, x11Decl, x11Ref);

            var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
            var x12Ref = GetReferences(tree, "x12").ToArray();
            Assert.Equal(2, x12Ref.Length);
            VerifyModelForOutVar(model, x12Decl, x12Ref);
        }

        [Fact]
        public void Scope_LabeledStatement_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        if (true)
a:          Dummy(TakeOutParam(true, out var x1));

        x1++;
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (13,1): error CS1023: Embedded statement cannot be a declaration or labeled statement
                // a:          Dummy(TakeOutParam(true, out var x1));
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "a:          Dummy(TakeOutParam(true, out var x1));").WithLocation(13, 1),
                // (15,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(15, 9),
                // (13,1): warning CS0164: This label has not been referenced
                // a:          Dummy(TakeOutParam(true, out var x1));
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(13, 1)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0]);
            VerifyNotInScope(model, x1Ref[0]);
        }

        [Fact]
        public void Scope_LabeledStatement_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (LabeledStatementSyntax)SyntaxFactory.ParseStatement(@"
a: b: Dummy(TakeOutParam(true, out var x1), x1);
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());
        }

        [Fact]
        public void Labeled_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test0();
    }

    static object Test0()
    {
a: b: c:Test2(Test1(out int x1), x1);
        System.Console.Write(x1);
        return null;
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }

    static object Test2(object x, object y)
    {
        System.Console.Write(y);
        return x;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: "11").VerifyDiagnostics(
                // (11,1): warning CS0164: This label has not been referenced
                // a: b: c:Test2(Test1(out int x1), x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(11, 1),
                // (11,4): warning CS0164: This label has not been referenced
                // a: b: c:Test2(Test1(out int x1), x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(11, 4),
                // (11,7): warning CS0164: This label has not been referenced
                // a: b: c:Test2(Test1(out int x1), x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(11, 7)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void Labeled_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test0();
    }

    static object Test0()
    {
        bool test = true;

        if (test)
        {
a:          Test2(Test1(out int x1), x1);
        }

        return null;
    }

    static object Test1(out int x)
    {
        x = 1;
        return null;
    }

    static object Test2(object x, object y)
    {
        System.Console.Write(y);
        return x;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: "1").VerifyDiagnostics(
                // (15,1): warning CS0164: This label has not been referenced
                // a:          Test2(Test1(out int x1), x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(15, 1)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void DataFlow_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test(out int x1, 
                     x1);
    }

    static void Test(out int x, int y)
    {
        x = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,22): error CS0165: Use of unassigned local variable 'x1'
                //                      x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(7, 22)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void DataFlow_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test(out int x1, 
                 ref x1);
    }

    static void Test(out int x, ref int y)
    {
        x = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,22): error CS0165: Use of unassigned local variable 'x1'
                //                  ref x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(7, 22)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void DataFlow_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test(out int x1);
        var x2 = 1;
    }

    static void Test(out int x)
    {
        x = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,13): warning CS0219: The variable 'x2' is assigned but its value is never used
                //         var x2 = 1;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x2").WithArguments("x2").WithLocation(7, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);

            var x2Decl = tree.GetRoot().DescendantNodes().OfType<LocalDeclarationStatementSyntax>().Single();

            var dataFlow = model.AnalyzeDataFlow(x2Decl);

            Assert.True(dataFlow.Succeeded);
            Assert.Equal("System.Int32 x2", dataFlow.VariablesDeclared.Single().ToTestDisplayString());
            Assert.Equal("System.Int32 x1", dataFlow.WrittenOutside.Single().ToTestDisplayString());
        }

        [Fact]
        public void TypeMismatch_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test(out int x1);
    }

    static void Test(out short x)
    {
        x = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,18): error CS1503: Argument 1: cannot convert from 'out int' to 'out short'
                //         Test(out int x1);
                Diagnostic(ErrorCode.ERR_BadArgType, "int x1").WithArguments("1", "out int", "out short").WithLocation(6, 18)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);
        }

        [Fact]
        public void Parse_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test(int x1);
        Test(ref int x2);
    }

    static void Test(out int x)
    {
        x = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,14): error CS1525: Invalid expression term 'int'
                //         Test(int x1);
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, "int").WithArguments("int").WithLocation(6, 14),
                // (6,18): error CS1003: Syntax error, ',' expected
                //         Test(int x1);
                Diagnostic(ErrorCode.ERR_SyntaxError, "x1").WithArguments(",").WithLocation(6, 18),
                // (7,18): error CS1525: Invalid expression term 'int'
                //         Test(ref int x2);
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, "int").WithArguments("int").WithLocation(7, 18),
                // (7,22): error CS1003: Syntax error, ',' expected
                //         Test(ref int x2);
                Diagnostic(ErrorCode.ERR_SyntaxError, "x2").WithArguments(",").WithLocation(7, 22),
                // (6,18): error CS0103: The name 'x1' does not exist in the current context
                //         Test(int x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(6, 18),
                // (7,22): error CS0103: The name 'x2' does not exist in the current context
                //         Test(ref int x2);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x2").WithArguments("x2").WithLocation(7, 22)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            Assert.False(GetOutVarDeclarations(tree).Any());
        }

        [Fact]
        public void Parse_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test(out int x1.);
    }

    static void Test(out int x)
    {
        x = 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,24): error CS1003: Syntax error, ',' expected
                //         Test(out int x1.);
                Diagnostic(ErrorCode.ERR_SyntaxError, ".").WithArguments(",").WithLocation(6, 24)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);
        }

        [Fact]
        public void Parse_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test(out System.Collections.Generic.IEnumerable<System.Int32>);
    }

    static void Test(out System.Collections.Generic.IEnumerable<System.Int32> x)
    {
        x = null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,18): error CS0118: 'IEnumerable<int>' is a type but is used like a variable
                //         Test(out System.Collections.Generic.IEnumerable<System.Int32>);
                Diagnostic(ErrorCode.ERR_BadSKknown, "System.Collections.Generic.IEnumerable<System.Int32>").WithArguments("System.Collections.Generic.IEnumerable<int>", "type", "variable").WithLocation(6, 18)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            Assert.False(GetOutVarDeclarations(tree).Any());
        }

        [Fact]
        public void GetAliasInfo_01()
        {
            var text = @"
using @a = System.Int32;

public class Cls
{
    public static void Main()
    {
        Test1(out a x1);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);

            Assert.Equal("a=System.Int32", model.GetAliasInfo(x1Decl.Type).ToTestDisplayString());
        }

        [Fact]
        public void GetAliasInfo_02()
        {
            var text = @"
using @var = System.Int32;

public class Cls
{
    public static void Main()
    {
        Test1(out var x1);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);

            Assert.Equal("var=System.Int32", model.GetAliasInfo(x1Decl.Type).ToTestDisplayString());
        }

        [Fact]
        public void VarIsNotVar_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out var x1), x1);
    }

    static object Test1(out var x)
    {
        x = new var() {val = 123};
        return null;
    }

    static void Test2(object x, var y)
    {
        System.Console.WriteLine(y.val);
    }

    struct @var
    {
        public int val;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void VarIsNotVar_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out var x1);
    }

    struct @var
    {
        public int val;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,9): error CS0103: The name 'Test1' does not exist in the current context
                //         Test1(out var x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "Test1").WithArguments("Test1").WithLocation(6, 9),
                // (11,20): warning CS0649: Field 'Cls.var.val' is never assigned to, and will always have its default value 0
                //         public int val;
                Diagnostic(ErrorCode.WRN_UnassignedInternalField, "val").WithArguments("Cls.var.val", "0").WithLocation(11, 20)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);

            Assert.Equal("Cls.var", ((ILocalSymbol)model.GetDeclaredSymbol(GetVariableDesignation(x1Decl))).Type.ToTestDisplayString());
        }

        [Fact]
        public void SimpleVar_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out var x1), x1);
    }

    static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
        }

        [Fact]
        public void SimpleVar_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out var x1), x1);
    }

    static void Test2(object x, object y)
    {
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,15): error CS0103: The name 'Test1' does not exist in the current context
                //         Test2(Test1(out var x1), x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "Test1").WithArguments("Test1").WithLocation(6, 15)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
        }

        [Fact]
        public void SimpleVar_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out var x1, 
                  out x1);
    }

    static object Test1(out int x, out int x2)
    {
        x = 123;
        x2 = 124;
        return null;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,23): error CS8181: Reference to an implicitly-typed out variable 'x1' is not permitted in this location.
                //                   out x1);
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableUsedInForbiddenZone, "x1").WithArguments("x1").WithLocation(7, 23)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
            Assert.Equal("System.Int32 x1", model.GetDeclaredSymbol(GetVariableDesignation(x1Decl)).ToTestDisplayString());
        }

        [Fact]
        public void SimpleVar_04()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out var x1, 
              Test1(out x1,
                    3));
    }

    static object Test1(out int x, int x2)
    {
        x = 123;
        x2 = 124;
        return null;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,25): error CS8181: Reference to an implicitly-typed out variable 'x1' is not permitted in this location.
                //               Test1(out x1,
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableUsedInForbiddenZone, "x1").WithArguments("x1").WithLocation(7, 25)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
            Assert.Equal("System.Int32 x1", model.GetDeclaredSymbol(GetVariableDesignation(x1Decl)).ToTestDisplayString());
        }

        [Fact]
        public void SimpleVar_05()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out var x1), x1);
    }

    static object Test1(ref int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,25): error CS1620: Argument 1 must be passed with the 'ref' keyword
                //         Test2(Test1(out var x1), x1);
                Diagnostic(ErrorCode.ERR_BadArgRef, "var x1").WithArguments("1", "ref").WithLocation(6, 25)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
            Assert.Equal("System.Int32 x1", model.GetDeclaredSymbol(GetVariableDesignation(x1Decl)).ToTestDisplayString());
        }

        [Fact]
        public void SimpleVar_06()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out var x1), x1);
    }

    static object Test1(int x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,25): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //         Test2(Test1(out var x1), x1);
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x1").WithArguments("1", "out").WithLocation(6, 25)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
            Assert.Equal("System.Int32 x1", model.GetDeclaredSymbol(GetVariableDesignation(x1Decl)).ToTestDisplayString());
        }

        [Fact]
        public void SimpleVar_07()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        dynamic x = null;
        Test2(x.Test1(out var x1), 
              x1);
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,31): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                //         Test2(x.Test1(out var x1), 
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(7, 31)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
            Assert.Equal("var x1", model.GetDeclaredSymbol(GetVariableDesignation(x1Decl)).ToTestDisplayString());
        }

        [Fact]
        public void SimpleVar_08()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(new Test1(out var x1), x1);
    }

    class Test1
    {
        public Test1(out int x)
        {
            x = 123;
        }
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void SimpleVar_09()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(new System.Action(out var x1), 
              x1);
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,37): error CS0149: Method name expected
                //         Test2(new System.Action(out var x1), 
                Diagnostic(ErrorCode.ERR_MethodNameExpected, "var x1").WithLocation(6, 37)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, isDelegateCreation: true, isExecutableCode: true, isShadowed: false, verifyDataFlow: true, references: x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
            Assert.Equal("var x1", model.GetDeclaredSymbol(GetVariableDesignation(x1Decl)).ToTestDisplayString());
        }

        [Fact]
        public void ConstructorInitializers_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        Test2(object x, object y)
        {
            System.Console.WriteLine(y);
        }

        public Test2()
        : this(Test1(out var x1), x1)
        {}
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Equal("System.Int32", ((ILocalSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(GetVariableDesignation(x1Decl))).Type.ToTestDisplayString());

            CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular7_2).VerifyDiagnostics(
                // (25,26): error CS8320: Feature 'declaration of expression variables in member initializers and queries' is not available in C# 7.2. Please use language version 7.3 or greater.
                //         : this(Test1(out var x1), x1)
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion7_2, "var x1").WithArguments("declaration of expression variables in member initializers and queries", "7.3").WithLocation(25, 26)
                );

            var initializer = tree.GetRoot().DescendantNodes().OfType<ConstructorInitializerSyntax>().Single();
            var typeInfo = model.GetTypeInfo(initializer);
            var symbolInfo = model.GetSymbolInfo(initializer);
            var group = model.GetMemberGroup(initializer);

            Assert.Equal("System.Void", typeInfo.Type.ToTestDisplayString());
            Assert.Equal("Cls.Test2..ctor(System.Object x, System.Object y)", symbolInfo.Symbol.ToTestDisplayString());
            Assert.Empty(group); // https://github.com/dotnet/roslyn/issues/24936
        }

        [Fact]
        public void ConstructorInitializers_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test3());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        public Test2(object x, object y)
        {
            System.Console.WriteLine(y);
        }
    }
    
    class Test3 : Test2
    {

        public Test3()
        : base(Test1(out var x1), x1)
        {}
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Equal("System.Int32", ((ILocalSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(GetVariableDesignation(x1Decl))).Type.ToTestDisplayString());

            CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular7_2).VerifyDiagnostics(
                // (29,26): error CS8320: Feature 'declaration of expression variables in member initializers and queries' is not available in C# 7.2. Please use language version 7.3 or greater.
                //         : base(Test1(out var x1), x1)
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion7_2, "var x1").WithArguments("declaration of expression variables in member initializers and queries", "7.3").WithLocation(29, 26)
                );
        }

        [Fact]
        public void ConstructorInitializers_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    class Test2
    {
        Test2(out int x)
        {
            x = 2;
        }

        public Test2()
        : this(out var x1)
        {
            System.Console.WriteLine(x1);
        }
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"2").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Equal("System.Int32", ((ILocalSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(GetVariableDesignation(x1Decl))).Type.ToTestDisplayString());
        }

        [Fact]
        public void ConstructorInitializers_04()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test3());
    }

    static void Do(object x){}

    class Test2
    {
        public Test2(out int x)
        {
            x = 1;
        }
    }
    
    class Test3 : Test2
    {

        public Test3()
        : base(out var x1)
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Equal("System.Int32", ((ILocalSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(GetVariableDesignation(x1Decl))).Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
        public void ConstructorInitializers_05()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        Test2(System.Func<object> x)
        {
            System.Console.WriteLine(x());
        }

        public Test2()
        : this(() =>
               {
                    Test1(out var x1);
                    return x1;
               })
        {}
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_06()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        Test2(object x)
        {
        }

        public Test2()
        : this(Test1(out var x1))
        {
            System.Console.WriteLine(x1);
        }
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_07()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        Test2(object x)
        {
        }

        public Test2()
        : this(Test1(out var x1))
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_08()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        Test2(object x)
        {
        }

        public Test2()
        : this(Test1(out var x1))
        {
            System.Console.WriteLine(x1);
        }
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (23,9): error CS8057: Block bodies and expression bodies cannot both be provided.
                //         public Test2()
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"public Test2()
        : this(Test1(out var x1))
        {
            System.Console.WriteLine(x1);
        }
        => System.Console.WriteLine(x1);").WithLocation(23, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var analyzer = new ConstructorInitializers_08_SyntaxAnalyzer();
            CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular)
                .GetAnalyzerDiagnostics(new[] { analyzer }, null).Verify();

            Assert.True(analyzer.ActionFired);
        }

        private class ConstructorInitializers_08_SyntaxAnalyzer : DiagnosticAnalyzer
        {
            public bool ActionFired { get; private set; }

            private static readonly DiagnosticDescriptor Descriptor =
               new DiagnosticDescriptor("XY0000", "Test", "Test", "Test", DiagnosticSeverity.Warning, true, "Test", "Test");

            public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics
            => ImmutableArray.Create(Descriptor);

            public override void Initialize(AnalysisContext context)
            {
                context.RegisterSyntaxNodeAction(Handle, SyntaxKind.ThisConstructorInitializer);
            }

            private void Handle(SyntaxNodeAnalysisContext context)
            {
                ActionFired = true;
                var tree = context.Node.SyntaxTree;
                var model = context.SemanticModel;
                var constructorDeclaration = (ConstructorDeclarationSyntax)context.Node.Parent;
                SyntaxTreeSemanticModel syntaxTreeModel = ((SyntaxTreeSemanticModel)model);

                Assert.True(syntaxTreeModel.TestOnlyMemberModels.ContainsKey(constructorDeclaration));

                MemberSemanticModel mm = syntaxTreeModel.TestOnlyMemberModels[constructorDeclaration];

                Assert.False(mm.TestOnlyTryGetBoundNodesFromMap(constructorDeclaration).IsEmpty);
                Assert.False(mm.TestOnlyTryGetBoundNodesFromMap(constructorDeclaration.Initializer).IsEmpty);
                Assert.False(mm.TestOnlyTryGetBoundNodesFromMap(constructorDeclaration.Body).IsEmpty);
                Assert.False(mm.TestOnlyTryGetBoundNodesFromMap(constructorDeclaration.ExpressionBody).IsEmpty);

                var x1Decl = GetOutVarDeclaration(tree, "x1");
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                Assert.Same(mm, syntaxTreeModel.GetMemberModel(x1Decl));
                Assert.Same(mm, syntaxTreeModel.GetMemberModel(x1Ref[0]));
                Assert.Same(mm, syntaxTreeModel.GetMemberModel(x1Ref[1]));
            }
        }

        [Fact]
        public void ConstructorInitializers_09()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
    }

    public static bool Test1(out int x)
    {
        throw null;
    }

    class Test2
    {
        Test2(bool x, int y)
        {
        }

        public Test2(bool a)
        : this(a && Test1(out var x1), x1)
        {
        }
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (20,40): error CS0165: Use of unassigned local variable 'x1'
                //         : this(a && Test1(out var x1), x1)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(20, 40)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_10()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
    }

    public static bool Test1(out int x)
    {
        throw null;
    }

    class Test2
    {
        Test2(bool x, int y)
        {
        }

        public Test2(bool a)
        : this(a && Test1(out var x1), 1)
        {
            System.Console.WriteLine(x1);
        }
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (22,38): error CS0165: Use of unassigned local variable 'x1'
                //             System.Console.WriteLine(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(22, 38)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_11()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
    }

    public static bool Test1(out int x)
    {
        throw null;
    }

    class Test2
    {
        Test2(bool x, int y)
        {
        }

        public Test2(bool a)
        : this(a && Test1(out var x1), 1)
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (21,37): error CS0165: Use of unassigned local variable 'x1'
                //         => System.Console.WriteLine(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(21, 37)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_12()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
    }

    public static bool Test1(out int x)
    {
        throw null;
    }

    class Test2
    {
        Test2(bool x, int y)
        {
        }

        public Test2(bool a)
        : this(a && Test1(out var x1), 1)
        {
            System.Console.WriteLine(x1);
        }
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (19,9): error CS8057: Block bodies and expression bodies cannot both be provided.
                //         public Test2(bool a)
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"public Test2(bool a)
        : this(a && Test1(out var x1), 1)
        {
            System.Console.WriteLine(x1);
        }
        => System.Console.WriteLine(x1);").WithLocation(19, 9),
                // (22,38): error CS0165: Use of unassigned local variable 'x1'
                //             System.Console.WriteLine(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(22, 38)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_13()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
    }

    public static bool Test1(out int x)
    {
        throw null;
    }

    class Test2
    {
        Test2(bool x, int y)
        {
        }

        public Test2(bool a)
        : this(a && Test1(out var x1), x1)
        {
            System.Console.WriteLine(x1);
        }
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (20,40): error CS0165: Use of unassigned local variable 'x1'
                //         : this(a && Test1(out var x1), x1)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(20, 40)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_14()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
    }

    public static bool Test1(out int x)
    {
        throw null;
    }

    class Test2
    {
        Test2(bool x, int y)
        {
        }

        public Test2(bool a)
        : this(a && Test1(out var x1), x1)
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (20,40): error CS0165: Use of unassigned local variable 'x1'
                //         : this(a && Test1(out var x1), x1)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(20, 40)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_15()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
    }

    public static bool Test1(out int x)
    {
        throw null;
    }

    class Test2
    {
        Test2(bool x, int y)
        {
        }

        public Test2(bool a)
        : this(a && Test1(out var x1), x1)
        {
            System.Console.WriteLine(x1);
        }
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (19,9): error CS8057: Block bodies and expression bodies cannot both be provided.
                //         public Test2(bool a)
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"public Test2(bool a)
        : this(a && Test1(out var x1), x1)
        {
            System.Console.WriteLine(x1);
        }
        => System.Console.WriteLine(x1);").WithLocation(19, 9),
                // (20,40): error CS0165: Use of unassigned local variable 'x1'
                //         : this(a && Test1(out var x1), x1)
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(20, 40)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_16()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        Test2(object a, object b, ref int x)
        {
            System.Console.WriteLine(x);
            x++;
        }

        public Test2()
        : this(Test1(out var x1), ((System.Func<int>)(() => x1++))(), ref x1)
        {
            System.Console.WriteLine(x1);
        }
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"124
125").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ConstructorInitializers_17()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Do(new Test2());
    }

    static void Do(object x){}

    public static object Test1(out int x)
    {
        x = 123;
        return null;
    }

    class Test2
    {
        Test2(object a, object b, ref int x)
        {
            System.Console.WriteLine(x);
            x++;
        }

        public Test2()
        : this(Test1(out var x1), ((System.Func<int>)(() => x1++))(), ref x1)
        => System.Console.WriteLine(x1);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"124
125").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void SimpleVar_14()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out var x1), x1);
    }

    static object Test1(out dynamic x)
    {
        x = 123;
        return null;
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            references: new MetadataReference[] { CSharpRef },
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
            Assert.Equal("dynamic x1", model.GetDeclaredSymbol(GetVariableDesignation(x1Decl)).ToTestDisplayString());
        }

        [Fact]
        public void SimpleVar_15()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(new Test1(out var var), var);
    }

    class Test1
    {
        public Test1(out int x)
        {
            x = 123;
        }
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var varDecl = GetOutVarDeclaration(tree, "var");
            var varRef = GetReferences(tree, "var").Skip(1).Single();
            VerifyModelForOutVar(model, varDecl, varRef);
        }

        [Fact]
        public void SimpleVar_16()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        if (Test1(out var x1))
        {
            System.Console.WriteLine(x1);
        }
    }

    static bool Test1(out int x)
    {
        x = 123;
        return true;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");

            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref).Type.ToTestDisplayString());

            VerifyModelForOutVar(model, x1Decl, x1Ref);

            Assert.Null(model.GetAliasInfo(x1Decl.Type));
        }

        [Fact]
        public void VarAndBetterness_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out var x1, null);
        Test2(out var x2, null);
    }

    static object Test1(out int x, object y)
    {
        x = 123;
        System.Console.WriteLine(x);
        return null;
    }

    static object Test1(out short x, string y)
    {
        x = 124;
        System.Console.WriteLine(x);
        return null;
    }

    static object Test2(out int x, string y)
    {
        x = 125;
        System.Console.WriteLine(x);
        return null;
    }

    static object Test2(out short x, object y)
    {
        x = 126;
        System.Console.WriteLine(x);
        return null;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput:
@"124
125").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);

            var x2Decl = GetOutVarDeclaration(tree, "x2");
            VerifyModelForOutVar(model, x2Decl);
        }

        [Fact]
        public void VarAndBetterness_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out var x1, null);
    }

    static object Test1(out int x, object y)
    {
        x = 123;
        System.Console.WriteLine(x);
        return null;
    }

    static object Test1(out short x, object y)
    {
        x = 124;
        System.Console.WriteLine(x);
        return null;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,9): error CS0121: The call is ambiguous between the following methods or properties: 'Cls.Test1(out int, object)' and 'Cls.Test1(out short, object)'
                //         Test1(out var x1, null);
                Diagnostic(ErrorCode.ERR_AmbigCall, "Test1").WithArguments("Cls.Test1(out int, object)", "Cls.Test1(out short, object)").WithLocation(6, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVar(model, x1Decl);
        }

        [ConditionalFact(typeof(DesktopOnly), Reason = ConditionalSkipReason.RestrictedTypesNeedDesktop)]
        public void RestrictedTypes_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out var x1), x1);
    }

    static object Test1(out System.ArgIterator x)
    {
        x = default(System.ArgIterator);
        return null;
    }

    static void Test2(object x, System.ArgIterator y)
    {
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,25): error CS1601: Cannot make reference to variable of type 'ArgIterator'
                //     static object Test1(out System.ArgIterator x)
                Diagnostic(ErrorCode.ERR_MethodArgCantBeRefAny, "out System.ArgIterator x").WithArguments("System.ArgIterator").WithLocation(9, 25)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [ConditionalFact(typeof(DesktopOnly), Reason = ConditionalSkipReason.RestrictedTypesNeedDesktop)]
        public void RestrictedTypes_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test2(Test1(out System.ArgIterator x1), x1);
    }

    static object Test1(out System.ArgIterator x)
    {
        x = default(System.ArgIterator);
        return null;
    }

    static void Test2(object x, System.ArgIterator y)
    {
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,25): error CS1601: Cannot make reference to variable of type 'ArgIterator'
                //     static object Test1(out System.ArgIterator x)
                Diagnostic(ErrorCode.ERR_MethodArgCantBeRefAny, "out System.ArgIterator x").WithArguments("System.ArgIterator").WithLocation(9, 25)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [ConditionalFact(typeof(DesktopOnly), Reason = ConditionalSkipReason.RestrictedTypesNeedDesktop)]
        public void RestrictedTypes_03()
        {
            var text = @"
public class Cls
{
    public static void Main() {}

    async void Test()
    {
        Test2(Test1(out var x1), x1);
    }

    static object Test1(out System.ArgIterator x)
    {
        x = default(System.ArgIterator);
        return null;
    }

    static void Test2(object x, System.ArgIterator y)
    {
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (11,25): error CS1601: Cannot make reference to variable of type 'ArgIterator'
                //     static object Test1(out System.ArgIterator x)
                Diagnostic(ErrorCode.ERR_MethodArgCantBeRefAny, "out System.ArgIterator x").WithArguments("System.ArgIterator").WithLocation(11, 25)
            );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void RestrictedTypes_04()
        {
            var text = @"
public class Cls
{
    public static void Main() {}

    async void Test()
    {
        Test2(Test1(out System.ArgIterator x1), x1);
        var x = default(System.ArgIterator);
    }

    static object Test1(out System.ArgIterator x)
    {
        x = default(System.ArgIterator);
        return null;
    }

    static void Test2(object x, System.ArgIterator y)
    {
    }
}";
            var compilation = CreateCompilation(text,
                                                targetFramework: TargetFramework.Mscorlib461,
                                                options: TestOptions.ReleaseExe,
                                                parseOptions: TestOptions.Regular12);

            compilation.VerifyDiagnostics(
                // (12,25): error CS1601: Cannot make reference to variable of type 'ArgIterator'
                //     static object Test1(out System.ArgIterator x)
                Diagnostic(ErrorCode.ERR_MethodArgCantBeRefAny, "out System.ArgIterator x").WithArguments("System.ArgIterator").WithLocation(12, 25),
                // (8,25): error CS9202: Feature 'ref and unsafe in async and iterator methods' is not available in C# 12.0. Please use language version 13.0 or greater.
                //         Test2(Test1(out System.ArgIterator x1), x1);
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion12, "System.ArgIterator").WithArguments("ref and unsafe in async and iterator methods", "13.0").WithLocation(8, 25),
                // (9,9): error CS9202: Feature 'ref and unsafe in async and iterator methods' is not available in C# 12.0. Please use language version 13.0 or greater.
                //         var x = default(System.ArgIterator);
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion12, "var").WithArguments("ref and unsafe in async and iterator methods", "13.0").WithLocation(9, 9),
                // (9,13): warning CS0219: The variable 'x' is assigned but its value is never used
                //         var x = default(System.ArgIterator);
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x").WithArguments("x").WithLocation(9, 13)
            );

            compilation = CreateCompilation(text, targetFramework: TargetFramework.Mscorlib461);

            compilation.VerifyDiagnostics(
                // (12,25): error CS1601: Cannot make reference to variable of type 'ArgIterator'
                //     static object Test1(out System.ArgIterator x)
                Diagnostic(ErrorCode.ERR_MethodArgCantBeRefAny, "out System.ArgIterator x").WithArguments("System.ArgIterator").WithLocation(12, 25),
                // (9,13): warning CS0219: The variable 'x' is assigned but its value is never used
                //         var x = default(System.ArgIterator);
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x").WithArguments("x").WithLocation(9, 13)
            );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void ElementAccess_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        var x = new [] {1};
        Test2(x[out var x1]);
        Test2(x1);
        Test2(x[out var _]);
    }

    static void Test2(object x) { }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            Assert.True(compilation.GetSemanticModel(tree).GetTypeInfo(x1Ref).Type.TypeKind == TypeKind.Error);

            var model = compilation.GetSemanticModel(tree);
            VerifyModelForOutVarWithoutDataFlow(compilation.GetSemanticModel(tree), x1Decl, x1Ref);

            compilation.VerifyDiagnostics(
                // (7,21): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //         Test2(x[out var x1]);
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x1").WithArguments("1", "out").WithLocation(7, 21),
                // (7,25): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                //         Test2(x[out var x1]);
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(7, 25),
                // (9,21): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //         Test2(x[out var _]);
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var _").WithArguments("1", "out").WithLocation(9, 21),
                // (9,21): error CS8183: Cannot infer the type of implicitly-typed discard.
                //         Test2(x[out var _]);
                Diagnostic(ErrorCode.ERR_DiscardTypeInferenceFailed, "var _").WithLocation(9, 21)
                );
        }

        [Fact]
        public void PointerAccess_01()
        {
            var text = @"
public class Cls
{
    public static unsafe void Main()
    {
        int* p = (int*)0;
        Test2(p[out var x1]);
        Test2(x1);
    }

    static void Test2(object x) { }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe.WithAllowUnsafe(true),
                                                            parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            Assert.True(compilation.GetSemanticModel(tree).GetTypeInfo(x1Ref).Type.TypeKind == TypeKind.Error);

            var model = compilation.GetSemanticModel(tree);
            VerifyModelForOutVarWithoutDataFlow(compilation.GetSemanticModel(tree), x1Decl, x1Ref);

            compilation.VerifyDiagnostics(
                // (7,21): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //         Test2(p[out var x1]);
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x1").WithArguments("1", "out").WithLocation(7, 21),
                // (7,25): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                //         Test2(p[out var x1]);
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(7, 25)
                );
        }

        [Fact]
        public void ElementAccess_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        var x = new [] {1};
        Test2(x[out int x1], x1);
    }

    static void Test2(object x, object y)
    {
        System.Console.WriteLine(y);
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            compilation.VerifyDiagnostics(
                // (7,21): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //         Test2(x[out int x1], x1);
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "int x1").WithArguments("1", "out").WithLocation(7, 21),
                // (7,21): error CS0165: Use of unassigned local variable 'x1'
                //         Test2(x[out int x1], x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "int x1").WithArguments("x1").WithLocation(7, 21)
                );
        }

        [Fact]
        [WorkItem(12058, "https://github.com/dotnet/roslyn/issues/12058")]
        public void MissingArgumentAndNamedOutVarArgument()
        {
            var source =
@"class Program
{
    public static void Main(string[] args)
    {
        if (M(s: out var s))
        {
            string s2 = s;
        }
    }
    public static bool M(int i, out string s)
    {
        s = i.ToString();
        return true;
    }
}
";
            var compilation = CreateCompilation(source,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (5,13): error CS7036: There is no argument given that corresponds to the required parameter 'i' of 'Program.M(int, out string)'
                //         if (M(s: out var s))
                Diagnostic(ErrorCode.ERR_NoCorrespondingArgument, "M").WithArguments("i", "Program.M(int, out string)").WithLocation(5, 13)
                );
        }

        [Fact]
        [WorkItem(12266, "https://github.com/dotnet/roslyn/issues/12266")]
        public void LocalVariableTypeInferenceAndOutVar_01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        var y = Test1(out var x);
        System.Console.WriteLine(y);
    }

    static int Test1(out int x)
    {
        x = 123;
        return 124;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"124").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(12266, "https://github.com/dotnet/roslyn/issues/12266")]
        public void LocalVariableTypeInferenceAndOutVar_02()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        var y = Test1(out int x) + x;
        System.Console.WriteLine(y);
    }

    static int Test1(out int x)
    {
        x = 123;
        return 124;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"247").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(12266, "https://github.com/dotnet/roslyn/issues/12266")]
        public void LocalVariableTypeInferenceAndOutVar_03()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        var y = Test1(out var x) + x;
        System.Console.WriteLine(y);
    }

    static int Test1(out int x)
    {
        x = 123;
        return 124;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"247").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReference(tree, "y");

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(12266, "https://github.com/dotnet/roslyn/issues/12266")]
        public void LocalVariableTypeInferenceAndOutVar_04()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        for (var y = Test1(out var x) + x; y != 0 ; y = 0)
        {
            System.Console.WriteLine(y);
        }
    }

    static int Test1(out int x)
    {
        x = 123;
        return 124;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"247").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReferences(tree, "y").Last();

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(12266, "https://github.com/dotnet/roslyn/issues/12266")]
        public void LocalVariableTypeInferenceAndOutVar_05()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        foreach (var y in new [] {Test1(out var x) + x})
        {
            System.Console.WriteLine(y);
        }
    }

    static int Test1(out int x)
    {
        x = 123;
        return 124;
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);

            CompileAndVerify(compilation, expectedOutput: @"247").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yRef = GetReferences(tree, "y").Last();

            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(15732, "https://github.com/dotnet/roslyn/issues/15732")]
        public void LocalVariableTypeInferenceAndOutVar_06()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(x: 1, out var y);
        System.Console.WriteLine(y);
    }

    static void Test1(int x, ref int y)
    {
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular7_1);

            compilation.VerifyDiagnostics(
                // (6,21): error CS1738: Named argument specifications must appear after all fixed arguments have been specified. Please use language version 7.2 or greater to allow non-trailing named arguments.
                //         Test1(x: 1, out var y);
                Diagnostic(ErrorCode.ERR_NamedArgumentSpecificationBeforeFixedArgument, "out var y").WithArguments("7.2").WithLocation(6, 21),
                // (6,25): error CS1620: Argument 2 must be passed with the 'ref' keyword
                //         Test1(x: 1, out var y);
                Diagnostic(ErrorCode.ERR_BadArgRef, "var y").WithArguments("2", "ref").WithLocation(6, 25)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yDecl = GetDeclaration(tree, "y");
            VerifyModelForOutVar(model, yDecl, GetReferences(tree, "y").ToArray());
        }

        [Fact]
        [WorkItem(15732, "https://github.com/dotnet/roslyn/issues/15732")]
        public void LocalVariableTypeInferenceAndOutVar_07()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        int x = 0;
        Test1(y: ref x, y: out var y);
        System.Console.WriteLine(y);
    }

    static void Test1(int x, ref int y)
    {
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,9): error CS7036: There is no argument given that corresponds to the required parameter 'x' of 'Cls.Test1(int, ref int)'
                //         Test1(y: ref x, y: out var y);
                Diagnostic(ErrorCode.ERR_NoCorrespondingArgument, "Test1").WithArguments("x", "Cls.Test1(int, ref int)").WithLocation(7, 9));

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yDecl = GetDeclaration(tree, "y");
            var yRef = GetReferences(tree, "y").ToArray();
            Assert.Equal(3, yRef.Length);
            Assert.Equal("System.Console.WriteLine(y)", yRef[2].Parent.Parent.Parent.ToString());
            VerifyModelForOutVar(model, yDecl, yRef[2]);
        }

        [Fact, WorkItem(13219, "https://github.com/dotnet/roslyn/issues/13219")]
        public void IndexingDynamic()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        dynamic d = null;
        var x = d[out int z];
    }
}";
            // the C# dynamic binder does not support ref or out indexers, so we don't run this
            CompileAndVerify(text, references: new[] { CSharpRef }).VerifyIL("Cls.Main()",
@"{
  // Code size       87 (0x57)
  .maxstack  7
  .locals init (object V_0, //d
                int V_1) //z
  IL_0000:  ldnull
  IL_0001:  stloc.0
  IL_0002:  ldsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_0007:  brtrue.s   IL_003e
  IL_0009:  ldc.i4.0
  IL_000a:  ldtoken    ""Cls""
  IL_000f:  call       ""System.Type System.Type.GetTypeFromHandle(System.RuntimeTypeHandle)""
  IL_0014:  ldc.i4.2
  IL_0015:  newarr     ""Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo""
  IL_001a:  dup
  IL_001b:  ldc.i4.0
  IL_001c:  ldc.i4.0
  IL_001d:  ldnull
  IL_001e:  call       ""Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo.Create(Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)""
  IL_0023:  stelem.ref
  IL_0024:  dup
  IL_0025:  ldc.i4.1
  IL_0026:  ldc.i4.s   17
  IL_0028:  ldnull
  IL_0029:  call       ""Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo.Create(Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)""
  IL_002e:  stelem.ref
  IL_002f:  call       ""System.Runtime.CompilerServices.CallSiteBinder Microsoft.CSharp.RuntimeBinder.Binder.GetIndex(Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, System.Type, System.Collections.Generic.IEnumerable<Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo>)""
  IL_0034:  call       ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>>.Create(System.Runtime.CompilerServices.CallSiteBinder)""
  IL_0039:  stsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_003e:  ldsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_0043:  ldfld      ""<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic> System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>>.Target""
  IL_0048:  ldsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_004d:  ldloc.0
  IL_004e:  ldloca.s   V_1
  IL_0050:  callvirt   ""dynamic <>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>.Invoke(System.Runtime.CompilerServices.CallSite, dynamic, ref int)""
  IL_0055:  pop
  IL_0056:  ret
}");
        }

        [Fact]
        public void IndexingDynamicWithDiscard()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        dynamic d = null;
        var x = d[out int _];
    }
}";
            // the C# dynamic binder does not support ref or out indexers, so we don't run this
            CompileAndVerify(text, references: new[] { CSharpRef }).VerifyIL("Cls.Main()",
@"
{
  // Code size       87 (0x57)
  .maxstack  7
  .locals init (object V_0, //d
                int V_1)
  IL_0000:  ldnull
  IL_0001:  stloc.0
  IL_0002:  ldsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_0007:  brtrue.s   IL_003e
  IL_0009:  ldc.i4.0
  IL_000a:  ldtoken    ""Cls""
  IL_000f:  call       ""System.Type System.Type.GetTypeFromHandle(System.RuntimeTypeHandle)""
  IL_0014:  ldc.i4.2
  IL_0015:  newarr     ""Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo""
  IL_001a:  dup
  IL_001b:  ldc.i4.0
  IL_001c:  ldc.i4.0
  IL_001d:  ldnull
  IL_001e:  call       ""Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo.Create(Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)""
  IL_0023:  stelem.ref
  IL_0024:  dup
  IL_0025:  ldc.i4.1
  IL_0026:  ldc.i4.s   17
  IL_0028:  ldnull
  IL_0029:  call       ""Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo.Create(Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)""
  IL_002e:  stelem.ref
  IL_002f:  call       ""System.Runtime.CompilerServices.CallSiteBinder Microsoft.CSharp.RuntimeBinder.Binder.GetIndex(Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, System.Type, System.Collections.Generic.IEnumerable<Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo>)""
  IL_0034:  call       ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>>.Create(System.Runtime.CompilerServices.CallSiteBinder)""
  IL_0039:  stsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_003e:  ldsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_0043:  ldfld      ""<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic> System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>>.Target""
  IL_0048:  ldsfld     ""System.Runtime.CompilerServices.CallSite<<>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>> Cls.<>o__0.<>p__0""
  IL_004d:  ldloc.0
  IL_004e:  ldloca.s   V_1
  IL_0050:  callvirt   ""dynamic <>F{00000040}<System.Runtime.CompilerServices.CallSite, dynamic, int, dynamic>.Invoke(System.Runtime.CompilerServices.CallSite, dynamic, ref int)""
  IL_0055:  pop
  IL_0056:  ret
}
");
        }

        [Fact]
        public void IndexingDynamicWithVarDiscard()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        dynamic d = null;
        var x = d[out var _];
    }
}";
            // the C# dynamic binder does not support ref or out indexers, so we don't run this
            var comp = CreateCompilation(text, options: TestOptions.DebugDll, references: new[] { CSharpRef });
            comp.VerifyDiagnostics(
                // (7,23): error CS8183: Cannot infer the type of implicitly-typed discard.
                //         var x = d[out var _];
                Diagnostic(ErrorCode.ERR_DiscardTypeInferenceFailed, "var _").WithLocation(7, 23)
                );
        }

        [Fact]
        public void IndexingDynamicWithShortDiscard()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        dynamic d = null;
        var x = d[out _];
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe);
            compilation.VerifyDiagnostics(
                // (7,23): error CS8183: Cannot infer the type of implicitly-typed discard.
                //         var x = d[out _];
                Diagnostic(ErrorCode.ERR_DiscardTypeInferenceFailed, "_").WithLocation(7, 23)
                );
        }

        [Fact, WorkItem(13219, "https://github.com/dotnet/roslyn/issues/13219")]
        public void IndexingDynamicWithOutVar()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        dynamic d = null;
        var x = d[out var x1] + x1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            var x1 = (ILocalSymbol)model.GetDeclaredSymbol(GetVariableDesignation(x1Decl));
            Assert.True(x1.Type.IsErrorType());
            VerifyModelForOutVar(compilation.GetSemanticModel(tree), x1Decl, x1Ref);

            compilation.VerifyDiagnostics(
                // (7,27): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                //         var x = d[out var x1] + x1;
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(7, 27)
                );
        }

        [Fact, WorkItem(13219, "https://github.com/dotnet/roslyn/issues/13219")]
        public void IndexingDynamicWithOutInt()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        dynamic d = null;
        var x = d[out int x1] + x1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            var x1 = (ILocalSymbol)model.GetDeclaredSymbol(GetVariableDesignation(x1Decl));
            Assert.Equal("System.Int32", x1.Type.ToTestDisplayString());
            compilation.VerifyDiagnostics();
        }

        [ClrOnlyFact, WorkItem(13219, "https://github.com/dotnet/roslyn/issues/13219")]
        public void OutVariableDeclarationInIndex()
        {
            var source1 =
@".class interface public abstract import IA
{
  .custom instance void [mscorlib]System.Reflection.DefaultMemberAttribute::.ctor(string) = ( 01 00 04 49 74 65 6D 00 00 ) // ...Item..
  .custom instance void [mscorlib]System.Runtime.InteropServices.CoClassAttribute::.ctor(class [mscorlib]System.Type) = ( 01 00 01 41 00 00 )
  .custom instance void [mscorlib]System.Runtime.InteropServices.GuidAttribute::.ctor(string) = ( 01 00 24 31 36 35 46 37 35 32 44 2D 45 39 43 34 2D 34 46 37 45 2D 42 30 44 30 2D 43 44 46 44 37 41 33 36 45 32 31 31 00 00 )
  .method public abstract virtual instance int32 get_Item([out] int32& i) { }
  .method public abstract virtual instance void set_Item([out] int32& i, int32 v) { }
  .property instance int32 Item([out] int32&)
  {
    .get instance int32 IA::get_Item([out] int32&)
    .set instance void IA::set_Item([out] int32&, int32)
  }
  .method public abstract virtual instance int32 get_P([out] int32& i) { }
  .method public abstract virtual instance void set_P([out] int32& i, int32 v) { }
  .property instance int32 P([out] int32&)
  {
    .get instance int32 IA::get_P([out] int32&)
    .set instance void IA::set_P([out] int32&, int32)
  }
}
.class public A implements IA
{
  .custom instance void [mscorlib]System.Reflection.DefaultMemberAttribute::.ctor(string) = ( 01 00 04 49 74 65 6D 00 00 ) // ...Item..
  .method public hidebysig specialname rtspecialname instance void .ctor()
  {
    ret
  }
  // i = 1; return 2;
  .method public virtual instance int32 get_P([out] int32& i)
  {
    ldarg.1
    ldc.i4.1
    stind.i4
    ldc.i4.2
    ret
  }
  // i = 3; return;
  .method public virtual instance void set_P([out] int32& i, int32 v)
  {
    ldarg.1
    ldc.i4.3
    stind.i4
    ret
  }
  .property instance int32 P([out] int32&)
  {
    .get instance int32 A::get_P([out] int32&)
    .set instance void A::set_P([out] int32&, int32)
  }
  // i = 4; return 5;
  .method public virtual instance int32 get_Item([out] int32& i)
  {
    ldarg.1
    ldc.i4.4
    stind.i4
    ldc.i4.5
    ret
  }
  // i = 6; return;
  .method public virtual instance void set_Item([out] int32& i, int32 v)
  {
    ldarg.1
    ldc.i4.6
    stind.i4
    ret
  }
  .property instance int32 Item([out] int32&)
  {
    .get instance int32 A::get_Item([out] int32&)
    .set instance void A::set_Item([out] int32&, int32)
  }
}";
            var reference1 = CompileIL(source1);
            var source2Template =
@"using System;
class B
{{
    public static void Main()
    {{
        A a = new A();
        IA ia = a;
        Console.WriteLine(ia.P[out {0} x1] + "" "" + x1);
        ia.P[out {0} x2] = 4;
        Console.WriteLine(x2);
        Console.WriteLine(ia[out {0} x3] + "" "" + x3);
        ia[out {0} x4] = 4;
        Console.WriteLine(x4);
    }}
}}";
            string[] fillIns = new[] { "int", "var" };
            foreach (var fillIn in fillIns)
            {
                var source2 = string.Format(source2Template, fillIn);
                var compilation = CreateCompilation(source2, references: new[] { reference1 });
                var tree = compilation.SyntaxTrees[0];
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(1, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);
                Assert.Equal("System.Int32", compilation.GetSemanticModel(tree).GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").ToArray();
                Assert.Equal(1, x2Ref.Length);
                VerifyModelForOutVar(model, x2Decl, x2Ref);
                Assert.Equal("System.Int32", compilation.GetSemanticModel(tree).GetTypeInfo(x2Ref[0]).Type.ToTestDisplayString());

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").ToArray();
                Assert.Equal(1, x3Ref.Length);
                VerifyModelForOutVar(model, x3Decl, x3Ref);
                Assert.Equal("System.Int32", compilation.GetSemanticModel(tree).GetTypeInfo(x3Ref[0]).Type.ToTestDisplayString());

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(1, x4Ref.Length);
                VerifyModelForOutVar(model, x4Decl, x4Ref);
                Assert.Equal("System.Int32", compilation.GetSemanticModel(tree).GetTypeInfo(x4Ref[0]).Type.ToTestDisplayString());

                CompileAndVerify(source2, references: new[] { reference1 }, expectedOutput:
    @"2 1
3
5 4
6")
                .VerifyIL("B.Main()",
    @"{
  // Code size      113 (0x71)
  .maxstack  4
  .locals init (int V_0, //x1
                int V_1, //x2
                int V_2, //x3
                int V_3, //x4
                int V_4)
  IL_0000:  newobj     ""A..ctor()""
  IL_0005:  dup
  IL_0006:  ldloca.s   V_0
  IL_0008:  callvirt   ""int IA.P[out int].get""
  IL_000d:  stloc.s    V_4
  IL_000f:  ldloca.s   V_4
  IL_0011:  call       ""string int.ToString()""
  IL_0016:  ldstr      "" ""
  IL_001b:  ldloca.s   V_0
  IL_001d:  call       ""string int.ToString()""
  IL_0022:  call       ""string string.Concat(string, string, string)""
  IL_0027:  call       ""void System.Console.WriteLine(string)""
  IL_002c:  dup
  IL_002d:  ldloca.s   V_1
  IL_002f:  ldc.i4.4
  IL_0030:  callvirt   ""void IA.P[out int].set""
  IL_0035:  ldloc.1
  IL_0036:  call       ""void System.Console.WriteLine(int)""
  IL_003b:  dup
  IL_003c:  ldloca.s   V_2
  IL_003e:  callvirt   ""int IA.this[out int].get""
  IL_0043:  stloc.s    V_4
  IL_0045:  ldloca.s   V_4
  IL_0047:  call       ""string int.ToString()""
  IL_004c:  ldstr      "" ""
  IL_0051:  ldloca.s   V_2
  IL_0053:  call       ""string int.ToString()""
  IL_0058:  call       ""string string.Concat(string, string, string)""
  IL_005d:  call       ""void System.Console.WriteLine(string)""
  IL_0062:  ldloca.s   V_3
  IL_0064:  ldc.i4.4
  IL_0065:  callvirt   ""void IA.this[out int].set""
  IL_006a:  ldloc.3
  IL_006b:  call       ""void System.Console.WriteLine(int)""
  IL_0070:  ret
}");
            }
        }

        [ClrOnlyFact]
        public void OutVariableDiscardInIndex()
        {
            var source1 =
@".class interface public abstract import IA
{
  .custom instance void [mscorlib]System.Reflection.DefaultMemberAttribute::.ctor(string) = ( 01 00 04 49 74 65 6D 00 00 ) // ...Item..
  .custom instance void [mscorlib]System.Runtime.InteropServices.CoClassAttribute::.ctor(class [mscorlib]System.Type) = ( 01 00 01 41 00 00 )
  .custom instance void [mscorlib]System.Runtime.InteropServices.GuidAttribute::.ctor(string) = ( 01 00 24 31 36 35 46 37 35 32 44 2D 45 39 43 34 2D 34 46 37 45 2D 42 30 44 30 2D 43 44 46 44 37 41 33 36 45 32 31 31 00 00 )
  .method public abstract virtual instance int32 get_Item([out] int32& i) { }
  .method public abstract virtual instance void set_Item([out] int32& i, int32 v) { }
  .property instance int32 Item([out] int32&)
  {
    .get instance int32 IA::get_Item([out] int32&)
    .set instance void IA::set_Item([out] int32&, int32)
  }
  .method public abstract virtual instance int32 get_P([out] int32& i) { }
  .method public abstract virtual instance void set_P([out] int32& i, int32 v) { }
  .property instance int32 P([out] int32&)
  {
    .get instance int32 IA::get_P([out] int32&)
    .set instance void IA::set_P([out] int32&, int32)
  }
}
.class public A implements IA
{
  .custom instance void [mscorlib]System.Reflection.DefaultMemberAttribute::.ctor(string) = ( 01 00 04 49 74 65 6D 00 00 ) // ...Item..
  .method public hidebysig specialname rtspecialname instance void .ctor()
  {
    ret
  }
  // i = 1; System.Console.WriteLine(11); return 111;
  .method public virtual instance int32 get_P([out] int32& i)
  {
    ldarg.1
    ldc.i4.1
    stind.i4
    ldc.i4.s   11
    call       void [mscorlib]System.Console::WriteLine(int32)
    ldc.i4     0x06F
    ret
  }
  // i = 2; System.Console.Write(22); return;
  .method public virtual instance void set_P([out] int32& i, int32 v)
  {
    ldarg.1
    ldc.i4.2
    stind.i4
    ldc.i4.s   22
    call       void [mscorlib]System.Console::WriteLine(int32)
    ret
  }
  .property instance int32 P([out] int32&)
  {
    .get instance int32 A::get_P([out] int32&)
    .set instance void A::set_P([out] int32&, int32)
  }
  // i = 3; System.Console.WriteLine(33) return 333;
  .method public virtual instance int32 get_Item([out] int32& i)
  {
    ldarg.1
    ldc.i4.3
    stind.i4
    ldc.i4.s   33
    call       void [mscorlib]System.Console::WriteLine(int32)
    ldc.i4     0x14D
    ret
  }
  // i = 4; System.Console.WriteLine(44); return;
  .method public virtual instance void set_Item([out] int32& i, int32 v)
  {
    ldarg.1
    ldc.i4.4
    stind.i4
    ldc.i4.s   44
    call       void [mscorlib]System.Console::WriteLine(int32)
    ret
  }
  .property instance int32 Item([out] int32&)
  {
    .get instance int32 A::get_Item([out] int32&)
    .set instance void A::set_Item([out] int32&, int32)
  }
}";
            var reference1 = CompileIL(source1);
            var source2Template =
@"using System;
class B
{{
    public static void Main()
    {{
        A a = new A();
        IA ia = a;
        Console.WriteLine(ia.P[out {0} _]);
        ia.P[out {0} _] = 4;
        Console.WriteLine(ia[out {0} _]);
        ia[out {0} _] = 4;
    }}
}}";
            string[] fillIns = new[] { "int", "var", "" };
            foreach (var fillIn in fillIns)
            {
                var source2 = string.Format(source2Template, fillIn);
                var compilation = CreateCompilation(source2, references: new[] { reference1 }, options: TestOptions.DebugExe);

                CompileAndVerify(compilation, expectedOutput:
@"11
111
22
33
333
44")
                .VerifyIL("B.Main()",
@"
{
  // Code size       58 (0x3a)
  .maxstack  3
  .locals init (A V_0, //a
                IA V_1, //ia
                int V_2)
  IL_0000:  nop
  IL_0001:  newobj     ""A..ctor()""
  IL_0006:  stloc.0
  IL_0007:  ldloc.0
  IL_0008:  stloc.1
  IL_0009:  ldloc.1
  IL_000a:  ldloca.s   V_2
  IL_000c:  callvirt   ""int IA.P[out int].get""
  IL_0011:  call       ""void System.Console.WriteLine(int)""
  IL_0016:  nop
  IL_0017:  ldloc.1
  IL_0018:  ldloca.s   V_2
  IL_001a:  ldc.i4.4
  IL_001b:  callvirt   ""void IA.P[out int].set""
  IL_0020:  nop
  IL_0021:  ldloc.1
  IL_0022:  ldloca.s   V_2
  IL_0024:  callvirt   ""int IA.this[out int].get""
  IL_0029:  call       ""void System.Console.WriteLine(int)""
  IL_002e:  nop
  IL_002f:  ldloc.1
  IL_0030:  ldloca.s   V_2
  IL_0032:  ldc.i4.4
  IL_0033:  callvirt   ""void IA.this[out int].set""
  IL_0038:  nop
  IL_0039:  ret
}");
            }
        }

        [Fact]
        public void ElementAccess_04()
        {
            var text = @"
using System.Collections.Generic;
public class Cls
{
    public static void Main()
    {
        var list = new Dictionary<int, long>
        {
            [out var x1] = 3,
            [out var _] = 4,
            [out _] = 5
        };
        System.Console.Write(x1);
        System.Console.Write(_);

        {
            int _ = 1;
            var list2 = new Dictionary<int, long> { [out _] = 6 };
        }
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            Assert.Equal("System.Int32", compilation.GetSemanticModel(tree).GetTypeInfo(x1Ref).Type.ToTestDisplayString());
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            compilation.VerifyDiagnostics(
                // (9,18): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //             [out var x1] = 3,
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x1").WithArguments("1", "out").WithLocation(9, 18),
                // (10,18): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //             [out var _] = 4,
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var _").WithArguments("1", "out").WithLocation(10, 18),
                // (11,18): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //             [out _] = 5
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "_").WithArguments("1", "out").WithLocation(11, 18),
                // (14,30): error CS0103: The name '_' does not exist in the current context
                //         System.Console.Write(_);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "_").WithArguments("_").WithLocation(14, 30),
                // (18,58): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //             var list2 = new Dictionary<int, long> { [out _] = 6 };
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "_").WithArguments("1", "out").WithLocation(18, 58)
                );
        }

        [Fact]
        public void ElementAccess_05()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        int[out var x1] a = null; // fatal syntax error - 'out' is skipped
        int b(out var x2) = null; // parsed as a local function with syntax error
        int c[out var x3] = null; // fatal syntax error - 'out' is skipped

        int d, e(out var x4); // parsed as a broken bracketed argument list on the declarator
        x4 = 0;
    }
}";
            var compilation = CreateCompilation(text);
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            Assert.Equal(1, compilation.SyntaxTrees[0].GetRoot().DescendantNodesAndSelf().OfType<DeclarationExpressionSyntax>().Count());

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            Assert.True(compilation.GetSemanticModel(tree).GetTypeInfo(x4Ref).Type.TypeKind == TypeKind.Error);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref);

            compilation.VerifyDiagnostics(
                // (6,13): error CS1003: Syntax error, ',' expected
                //         int[out var x1] a = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_SyntaxError, "out").WithArguments(",").WithLocation(6, 13),
                // (6,21): error CS1003: Syntax error, ',' expected
                //         int[out var x1] a = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_SyntaxError, "x1").WithArguments(",").WithLocation(6, 21),
                // (7,27): error CS1002: ; expected
                //         int b(out var x2) = null; // parsed as a local function with syntax error
                Diagnostic(ErrorCode.ERR_SemicolonExpected, "=").WithLocation(7, 27),
                // (7,27): error CS1525: Invalid expression term '='
                //         int b(out var x2) = null; // parsed as a local function with syntax error
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, "=").WithArguments("=").WithLocation(7, 27),
                // (8,14): error CS0650: Bad array declarator: To declare a managed array the rank specifier precedes the variable's identifier. To declare a fixed size buffer field, use the fixed keyword before the field type.
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_CStyleArray, "[out var x3]").WithLocation(8, 14),
                // (8,15): error CS1003: Syntax error, ',' expected
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_SyntaxError, "out").WithArguments(",").WithLocation(8, 15),
                // (8,19): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "var").WithLocation(8, 19),
                // (8,23): error CS1003: Syntax error, ',' expected
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_SyntaxError, "x3").WithArguments(",").WithLocation(8, 23),
                // (8,23): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "x3").WithLocation(8, 23),
                // (10,17): error CS1528: Expected ; or = (cannot specify constructor arguments in declaration)
                //         int d, e(out var x4); // parsed as a broken bracketed argument list on the declarator
                Diagnostic(ErrorCode.ERR_BadVarDecl, "(out var x4").WithLocation(10, 17),
                // (10,17): error CS1003: Syntax error, '[' expected
                //         int d, e(out var x4); // parsed as a broken bracketed argument list on the declarator
                Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(10, 17),
                // (10,28): error CS1003: Syntax error, ']' expected
                //         int d, e(out var x4); // parsed as a broken bracketed argument list on the declarator
                Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(10, 28),
                // (6,12): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         int[out var x1] a = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[out var x1]").WithLocation(6, 12),
                // (6,17): error CS0103: The name 'var' does not exist in the current context
                //         int[out var x1] a = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(6, 17),
                // (6,21): error CS0103: The name 'x1' does not exist in the current context
                //         int[out var x1] a = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(6, 21),
                // (7,13): error CS8112: 'b(out var)' is a local function and must therefore always have a body.
                //         int b(out var x2) = null; // parsed as a local function with syntax error
                Diagnostic(ErrorCode.ERR_LocalFunctionMissingBody, "b").WithArguments("b(out var)").WithLocation(7, 13),
                // (7,19): error CS0825: The contextual keyword 'var' may only appear within a local variable declaration or in script code
                //         int b(out var x2) = null; // parsed as a local function with syntax error
                Diagnostic(ErrorCode.ERR_TypeVarNotFound, "var").WithLocation(7, 19),
                // (8,29): error CS0037: Cannot convert null to 'int' because it is a non-nullable value type
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_ValueCantBeNull, "null").WithArguments("int").WithLocation(8, 29),
                // (8,19): error CS0103: The name 'var' does not exist in the current context
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(8, 19),
                // (8,23): error CS0103: The name 'x3' does not exist in the current context
                //         int c[out var x3] = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x3").WithArguments("x3").WithLocation(8, 23),
                // (7,13): error CS0177: The out parameter 'x2' must be assigned to before control leaves the current method
                //         int b(out var x2) = null; // parsed as a local function with syntax error
                Diagnostic(ErrorCode.ERR_ParamUnassigned, "b").WithArguments("x2").WithLocation(7, 13),
                // (6,25): warning CS0219: The variable 'a' is assigned but its value is never used
                //         int[out var x1] a = null; // fatal syntax error - 'out' is skipped
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "a").WithArguments("a").WithLocation(6, 25),
                // (10,13): warning CS0168: The variable 'd' is declared but never used
                //         int d, e(out var x4); // parsed as a broken bracketed argument list on the declarator
                Diagnostic(ErrorCode.WRN_UnreferencedVar, "d").WithArguments("d").WithLocation(10, 13),
                // (10,16): warning CS0168: The variable 'e' is declared but never used
                //         int d, e(out var x4); // parsed as a broken bracketed argument list on the declarator
                Diagnostic(ErrorCode.WRN_UnreferencedVar, "e").WithArguments("e").WithLocation(10, 16),
                // (7,13): warning CS8321: The local function 'b' is declared but never used
                //         int b(out var x2) = null; // parsed as a local function with syntax error
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "b").WithArguments("b").WithLocation(7, 13)
                );
        }

        [Fact]
        public void ElementAccess_06()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        {
            int[] e = null;
            var z1 = e?[out var x1];
            x1 = 1;
        }
        {
            int[][] e = null;
            var z2 = e?[out var x2]?[out var x3];
            x2 = 1;
            x3 = 2;
        }
        {
            int[][] e = null;
            var z3 = e?[0]?[out var x4];
            x4 = 1;
        }
    }
}";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseExe,
                                                            parseOptions: TestOptions.Regular);
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            Assert.True(model.GetTypeInfo(x1Ref).Type.TypeKind == TypeKind.Error);
            var x2Decl = GetOutVarDeclaration(tree, "x2");
            var x2Ref = GetReference(tree, "x2");
            Assert.True(model.GetTypeInfo(x2Ref).Type.TypeKind == TypeKind.Error);
            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            Assert.True(model.GetTypeInfo(x3Ref).Type.TypeKind == TypeKind.Error);
            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            Assert.True(model.GetTypeInfo(x4Ref).Type.TypeKind == TypeKind.Error);

            VerifyModelForOutVarWithoutDataFlow(compilation.GetSemanticModel(tree), x1Decl, x1Ref);

            compilation.VerifyDiagnostics(
                // (8,29): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //             var z1 = e?[out var x1];
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x1").WithArguments("1", "out").WithLocation(8, 29),
                // (8,33): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                //             var z1 = e?[out var x1];
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(8, 33),
                // (13,29): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //             var z2 = e?[out var x2]?[out var x3];
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x2").WithArguments("1", "out").WithLocation(13, 29),
                // (13,33): error CS8197: Cannot infer the type of implicitly-typed out variable 'x2'.
                //             var z2 = e?[out var x2]?[out var x3];
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x2").WithArguments("x2").WithLocation(13, 33),
                // (19,33): error CS1615: Argument 1 may not be passed with the 'out' keyword
                //             var z3 = e?[0]?[out var x4];
                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "var x4").WithArguments("1", "out").WithLocation(19, 33),
                // (19,37): error CS8197: Cannot infer the type of implicitly-typed out variable 'x4'.
                //             var z3 = e?[0]?[out var x4];
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x4").WithArguments("x4").WithLocation(19, 37)
                );
        }

        [Fact]
        public void FixedFieldSize()
        {
            var text = @"
unsafe struct S
{
    fixed int F1[out var x1, x1];
    //fixed int F2[3 is int x2 ? x2 : 3];
    //fixed int F2[3 is int x3 ? 3 : 3, x3];
}
";
            var compilation = CreateCompilation(text,
                                                            options: TestOptions.ReleaseDebugDll.WithAllowUnsafe(true),
                                                            parseOptions: TestOptions.Regular);
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            Assert.Empty(GetOutVarDeclarations(tree, "x1"));

            compilation.VerifyDiagnostics(
                // (4,18): error CS1003: Syntax error, ',' expected
                //     fixed int F1[out var x1, x1];
                Diagnostic(ErrorCode.ERR_SyntaxError, "out").WithArguments(",").WithLocation(4, 18),
                // (4,26): error CS1003: Syntax error, ',' expected
                //     fixed int F1[out var x1, x1];
                Diagnostic(ErrorCode.ERR_SyntaxError, "x1").WithArguments(",").WithLocation(4, 26),
                // (4,17): error CS7092: A fixed buffer may only have one dimension.
                //     fixed int F1[out var x1, x1];
                Diagnostic(ErrorCode.ERR_FixedBufferTooManyDimensions, "[out var x1, x1]").WithLocation(4, 17),
                // (4,22): error CS0103: The name 'var' does not exist in the current context
                //     fixed int F1[out var x1, x1];
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(4, 22)
                );
        }

        [Fact]
        public void Scope_DeclaratorArguments_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        int d,e(Dummy(TakeOutParam(true, out var x1), x1));
    }
    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        int d,e(Dummy(TakeOutParam(true, out var x4), x4));
    }

    void Test6()
    {
        int d,e(Dummy(x6 && TakeOutParam(true, out var x6)));
    }

    void Test8()
    {
        int d,e(Dummy(TakeOutParam(true, out var x8), x8));
        System.Console.WriteLine(x8);
    }

    void Test14()
    {
        int d,e(Dummy(TakeOutParam(1, out var x14), 
                      TakeOutParam(2, out var x14), 
                      x14));
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.WRN_UnreferencedVar
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (19,50): error CS0128: A local variable named 'x4' is already defined in this scope
                //         int d,e(Dummy(TakeOutParam(true, out var x4), x4));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(19, 50),
                // (24,23): error CS0841: Cannot use local variable 'x6' before it is declared
                //         int d,e(Dummy(x6 && TakeOutParam(true, out var x6)));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(24, 23),
                // (30,34): error CS0165: Use of unassigned local variable 'x8'
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x8").WithArguments("x8").WithLocation(30, 34),
                // (36,47): error CS0128: A local variable named 'x14' is already defined in this scope
                //                       TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(36, 47)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyNotAnOutLocal(model, x4Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").Single();
            AssertContainedInDeclaratorArguments(x6Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x6Decl, x6Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(2, x8Ref.Length);
            AssertContainedInDeclaratorArguments(x8Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x8Decl, x8Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").Single();
            Assert.Equal(2, x14Decl.Length);
            AssertContainedInDeclaratorArguments(x14Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        private static void AssertContainedInDeclaratorArguments(DeclarationExpressionSyntax decl)
        {
            Assert.True(decl.Ancestors().OfType<VariableDeclaratorSyntax>().First().ArgumentList.Contains(decl));
        }

        private static void AssertNotContainedInDeclaratorArguments(DeclarationExpressionSyntax decl)
            => Assert.Empty(decl.Ancestors().OfType<VariableDeclaratorSyntax>());

        private static void AssertContainedInDeclaratorArguments(params DeclarationExpressionSyntax[] decls)
        {
            foreach (var decl in decls)
            {
                AssertContainedInDeclaratorArguments(decl);
            }
        }

        [Fact]
        public void Scope_DeclaratorArguments_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        var d, x1( 
                 Dummy(TakeOutParam(true, out var x1), x1));
        Dummy(x1);
    }

    void Test2()
    {
        object d, x2( 
                    Dummy(TakeOutParam(true, out var x2), x2));
        Dummy(x2);
    }

    void Test3()
    {
        object x3, d( 
                    Dummy(TakeOutParam(true, out var x3), x3));
        Dummy(x3);
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.WRN_UnreferencedVar
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (12,13): error CS0818: Implicitly-typed variables must be initialized
                //         var d, x1( 
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableWithNoInitializer, "d").WithLocation(12, 13),
                // (13,51): error CS0128: A local variable named 'x1' is already defined in this scope
                //                  Dummy(TakeOutParam(true, out var x1), x1));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 51),
                // (20,54): error CS0128: A local variable named 'x2' is already defined in this scope
                //                     Dummy(TakeOutParam(true, out var x2), x2));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 54),
                // (21,15): error CS0165: Use of unassigned local variable 'x2'
                //         Dummy(x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(21, 15),
                // (27,54): error CS0128: A local variable named 'x3' is already defined in this scope
                //                     Dummy(TakeOutParam(true, out var x3), x3));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(27, 54),
                // (28,15): error CS0165: Use of unassigned local variable 'x3'
                //         Dummy(x3);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x3").WithArguments("x3").WithLocation(28, 15)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x2Decl);
            VerifyNotAnOutLocal(model, x2Ref[0]);
            VerifyNotAnOutLocal(model, x2Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyNotAnOutLocal(model, x3Ref[0]);
            VerifyNotAnOutLocal(model, x3Ref[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x3Decl);
        }

        [Fact]
        public void Scope_DeclaratorArguments_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    object Dummy(params object[] x) {return null;}

    void Test1()
    {
        object d,e(Dummy(TakeOutParam(true, out var x1), x1)], 
               x1(  Dummy(x1));
        Dummy(x1);
    }

    void Test2()
    {
        object d1,e(Dummy(TakeOutParam(true, out var x2), x2)], 
                 d2(Dummy(TakeOutParam(true, out var x2), x2));
    }

    void Test3()
    {
        object d1,e(Dummy(TakeOutParam(true, out var x3), x3)], 
                 d2(Dummy(x3));
    }

    void Test4()
    {
        object d1,e(Dummy(x4)], 
                 d2(Dummy(TakeOutParam(true, out var x4), x4));
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.WRN_UnreferencedVar,
                                        (int)ErrorCode.ERR_CloseParenExpected
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (13,16): error CS0128: A local variable named 'x1' is already defined in this scope
                //                x1(  Dummy(x1));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 16),
                // (14,15): error CS0165: Use of unassigned local variable 'x1'
                //         Dummy(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(14, 15),
                // (20,54): error CS0128: A local variable named 'x2' is already defined in this scope
                //                  d2(Dummy(TakeOutParam(true, out var x2), x2));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 54),
                // (31,27): error CS0841: Cannot use local variable 'x4' before it is declared
                //         object d1,e(Dummy(x4)], 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(31, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x2Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl[0], x2Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl[1]);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref);
        }

        [Fact]
        public void Scope_DeclaratorArguments_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

   object Dummy(params object[] x) {return null;}

    void Test1()
    {
        object d,e(Dummy(TakeOutParam(true, out var x1), x1)], 
               x1 = Dummy(x1);
        Dummy(x1);
    }

    void Test2()
    {
        object d1,e(Dummy(TakeOutParam(true, out var x2), x2)], 
               d2 = Dummy(TakeOutParam(true, out var x2), x2);
    }

    void Test3()
    {
        object d1,e(Dummy(TakeOutParam(true, out var x3), x3)], 
               d2 = Dummy(x3);
    }

    void Test4()
    {
        object d1 = Dummy(x4), 
               d2  (Dummy(TakeOutParam(true, out var x4), x4));
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.ERR_UnexpectedToken,
                                        (int)ErrorCode.WRN_UnreferencedVar,
                                        (int)ErrorCode.ERR_CloseParenExpected
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (13,16): error CS0128: A local variable named 'x1' is already defined in this scope
                //                x1 = Dummy(x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 16),
                // (13,27): error CS0165: Use of unassigned local variable 'x1'
                //                x1 = Dummy(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(13, 27),
                // (20,54): error CS0128: A local variable named 'x2' is already defined in this scope
                //                d2 = Dummy(TakeOutParam(true, out var x2), x2);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 54),
                // (20,59): error CS0165: Use of unassigned local variable 'x2'
                //                d2 = Dummy(TakeOutParam(true, out var x2), x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(20, 59),
                // (26,27): error CS0165: Use of unassigned local variable 'x3'
                //                d2 = Dummy(x3);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x3").WithArguments("x3").WithLocation(26, 27),
                // (31,27): error CS0841: Cannot use local variable 'x4' before it is declared
                //         object d1 = Dummy(x4), 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(31, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x2Decl[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl[0], x2Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl[1]);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Ref.Length);
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref);
        }

        [Fact]
        public void Scope_DeclaratorArguments_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    long Dummy(params object[] x) {}

    void Test1()
    {
        SpeculateHere();
    }

    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var statement = (LocalDeclarationStatementSyntax)SyntaxFactory.ParseStatement(@"
var y, y1(Dummy(TakeOutParam(true, out var x1), x1));
");

            bool success = model.TryGetSpeculativeSemanticModel(GetReferences(tree, "SpeculateHere").Single().SpanStart, statement, out model);
            Assert.True(success);
            Assert.NotNull(model);
            tree = statement.SyntaxTree;

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);
            Assert.Equal("System.Int32", model.GetTypeInfo(x1Ref[0]).Type.ToTestDisplayString());

            var y1 = model.LookupSymbols(x1Ref[0].SpanStart, name: "y1").Single();
            Assert.Equal("var y1", y1.ToTestDisplayString());
            Assert.True(((ILocalSymbol)y1).Type.IsErrorType());
        }

        [Fact]
        public void Scope_DeclaratorArguments_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    void Test1()
    {
        if (true)
            var d,e(TakeOutParam(true, out var x1) && x1 != null);

        x1++;
    }

    static bool TakeOutParam(object y, out object x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.WRN_UnreferencedVar
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (11,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var d =TakeOutParam(true, out var x1) && x1 != null;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var d,e(TakeOutParam(true, out var x1) && x1 != null);").WithLocation(11, 13),
                // (11,17): error CS0818: Implicitly-typed variables must be initialized
                //             var d,e(TakeOutParam(true, out var x1) && x1 != null);
                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableWithNoInitializer, "d").WithLocation(11, 17),
                // (13,9): error CS0103: The name 'x1' does not exist in the current context
                //         x1++;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(13, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref[0]);
            VerifyNotInScope(model, x1Ref[1]);

            var e = tree.GetRoot().DescendantNodes().OfType<VariableDeclaratorSyntax>().Where(id => id.Identifier.ValueText == "e").Single();
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(e);
            Assert.Equal("var e", symbol.ToTestDisplayString());
            Assert.True(symbol.Type.IsErrorType());
        }

        [Fact]
        [WorkItem(13460, "https://github.com/dotnet/roslyn/issues/13460")]
        public void Scope_DeclaratorArguments_07()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        Test(1);
    }

    static void Test(int val)
    {
        switch (val)
        {
            case 1 when TakeOutParam(123, out var x1):
                var z, z1(x1, out var u1, x1 > 0 & TakeOutParam(x1, out var y1)];
                System.Console.WriteLine(y1);
                System.Console.WriteLine(z1 ? 1 : 0);
                break;
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var y1Decl = GetOutVarDeclarations(tree, "y1").Single();
            AssertContainedInDeclaratorArguments(y1Decl);

            var yRef = GetReference(tree, "y1");
            Assert.Equal("System.Int32", model.GetTypeInfo(yRef).Type.ToTestDisplayString());

            model = compilation.GetSemanticModel(tree);
            var zRef = GetReference(tree, "z1");
            Assert.True(((ITypeSymbol)model.GetTypeInfo(zRef).Type).IsErrorType());
        }

        [Fact]
        [WorkItem(13459, "https://github.com/dotnet/roslyn/issues/13459")]
        public void Scope_DeclaratorArguments_08()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test1()
    {
        for (bool a, b(
             Dummy(TakeOutParam(true, out var x1) && x1)
             );;)
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        for (bool a, b(
             Dummy(TakeOutParam(true, out var x2) && x2)
             );;)
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        for (bool a, b(
             Dummy(TakeOutParam(true, out var x4) && x4)
             );;)
            Dummy(x4);
    }

    void Test6()
    {
        for (bool a, b(
             Dummy(x6 && TakeOutParam(true, out var x6))
             );;)
            Dummy(x6);
    }

    void Test7()
    {
        for (bool a, b(
             Dummy(TakeOutParam(true, out var x7) && x7)
             );;)
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        for (bool a, b(
             Dummy(TakeOutParam(true, out var x8) && x8)
             );;)
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        for (bool a1, b1(
             Dummy(TakeOutParam(true, out var x9) && x9)
             );;)
        {   
            Dummy(x9);
            for (bool a2, b2(
                 Dummy(TakeOutParam(true, out var x9) && x9) // 2
                 );;)
                Dummy(x9);
        }
    }

    void Test10()
    {
        for (bool a, b(
             Dummy(TakeOutParam(y10, out var x10))
             );;)
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    for (bool a, b(
    //         Dummy(TakeOutParam(y11, out var x11))
    //         );;)
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        for (bool a, b(
             Dummy(TakeOutParam(y12, out var x12))
             );;)
            var y12 = 12;
    }

    //void Test13()
    //{
    //    for (bool a, b(
    //         Dummy(TakeOutParam(y13, out var x13))
    //         );;)
    //        let y13 = 12;
    //}

    void Test14()
    {
        for (bool a, b(
             Dummy(TakeOutParam(1, out var x14), 
                   TakeOutParam(2, out var x14), 
                   x14)
             );;)
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = [
                (int)ErrorCode.ERR_BadVarDecl,
                (int)ErrorCode.ERR_SyntaxError,
                (int)ErrorCode.ERR_UnexpectedToken,
                (int)ErrorCode.WRN_UnreferencedVar,
                (int)ErrorCode.ERR_UseDefViolation,
                (int)ErrorCode.ERR_SemicolonExpected,
                (int)ErrorCode.ERR_CloseParenExpected,
                (int)ErrorCode.ERR_InvalidExprTerm,
            ];

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (12,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(12, 22),
                // (22,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(22, 22),
                // (33,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(33, 22),
                // (34,47): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x4) && x4)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(34, 47),
                // (41,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(41, 22),
                // (42,20): error CS0841: Cannot use local variable 'x6' before it is declared
                //              Dummy(x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(42, 20),
                // (49,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(49, 22),
                // (53,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(53, 17),
                // (60,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(60, 22),
                // (65,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(65, 34),
                // (70,23): error CS0103: The name 'b1' does not exist in the current context
                //         for (bool a1, b1(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b1").WithArguments("b1").WithLocation(70, 23),
                // (75,27): error CS0103: The name 'b2' does not exist in the current context
                //             for (bool a2, b2(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b2").WithArguments("b2").WithLocation(75, 27),
                // (76,51): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                  Dummy(TakeOutParam(true, out var x9) && x9) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(76, 51),
                // (84,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(84, 22),
                // (85,33): error CS0103: The name 'y10' does not exist in the current context
                //              Dummy(TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(85, 33),
                // (106,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(106, 22),
                // (107,33): error CS0103: The name 'y12' does not exist in the current context
                //              Dummy(TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(107, 33),
                // (109,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(109, 13),
                // (109,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(109, 17),
                // (122,22): error CS0103: The name 'b' does not exist in the current context
                //         for (bool a, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(122, 22),
                // (124,44): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                    TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(124, 44));

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            AssertNotContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            AssertNotContainedInDeclaratorArguments(x2Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            AssertNotContainedInDeclaratorArguments(x4Decl);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            AssertNotContainedInDeclaratorArguments(x6Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            AssertNotContainedInDeclaratorArguments(x7Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            AssertNotContainedInDeclaratorArguments(x8Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            Assert.All(x9Decl, x9Decl => AssertNotContainedInDeclaratorArguments(x9Decl));
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            Assert.All(x14Decl, x14Decl => AssertNotContainedInDeclaratorArguments(x14Decl));
            VerifyModelForOutVarWithoutDataFlow(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_09()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(params object[] x) {return true;}

    void Test4()
    {
        for (bool d, x4(
             Dummy(TakeOutParam(true, out var x4) && x4)
             );;)
        {}
    }

    void Test7()
    {
        for (bool x7 = true, b(
             Dummy(TakeOutParam(true, out var x7) && x7)
             );;)
        {}
    }

    void Test8()
    {
        for (bool d,b1(Dummy(TakeOutParam(true, out var x8) && x8)], 
               b2(Dummy(TakeOutParam(true, out var x8) && x8));
             Dummy(TakeOutParam(true, out var x8) && x8);
             Dummy(TakeOutParam(true, out var x8) && x8))
        {}
    }

    void Test9()
    {
        for (bool b = x9, 
               b2(Dummy(TakeOutParam(true, out var x9) && x9));
             Dummy(TakeOutParam(true, out var x9) && x9);
             Dummy(TakeOutParam(true, out var x9) && x9))
        {}
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = [
                (int)ErrorCode.ERR_BadVarDecl,
                (int)ErrorCode.ERR_SyntaxError,
                (int)ErrorCode.ERR_UnexpectedToken,
                (int)ErrorCode.WRN_UnreferencedVar,
                (int)ErrorCode.ERR_CloseParenExpected,
                (int)ErrorCode.ERR_SemicolonExpected,
                (int)ErrorCode.ERR_InvalidExprTerm,
            ];

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (12,22): error CS0841: Cannot use local variable 'x4' before it is declared
                //         for (bool d, x4(
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(12, 22),
                // (20,30): error CS0103: The name 'b' does not exist in the current context
                //         for (bool x7 = true, b(
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b").WithArguments("b").WithLocation(20, 30),
                // (21,47): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x7) && x7)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(21, 47),
                // (20,19): warning CS0219: The variable 'x7' is assigned but its value is never used
                //         for (bool x7 = true, b(
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x7").WithArguments("x7").WithLocation(20, 19),
                // (28,21): error CS0103: The name 'b1' does not exist in the current context
                //         for (bool d,b1(Dummy(TakeOutParam(true, out var x8) && x8)], 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b1").WithArguments("b1").WithLocation(28, 21),
                // (29,16): error CS0103: The name 'b2' does not exist in the current context
                //                b2(Dummy(TakeOutParam(true, out var x8) && x8));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b2").WithArguments("b2").WithLocation(29, 16),
                // (29,52): error CS0136: A local or parameter named 'x8' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //                b2(Dummy(TakeOutParam(true, out var x8) && x8));
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x8").WithArguments("x8").WithLocation(29, 52),
                // (30,47): error CS0128: A local variable or function named 'x8' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x8) && x8);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(30, 47),
                // (31,47): error CS0128: A local variable or function named 'x8' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x8) && x8))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x8").WithArguments("x8").WithLocation(31, 47),
                // (37,23): error CS0103: The name 'x9' does not exist in the current context
                //         for (bool b = x9, 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x9").WithArguments("x9").WithLocation(37, 23),
                // (38,16): error CS0103: The name 'b2' does not exist in the current context
                //                b2(Dummy(TakeOutParam(true, out var x9) && x9));
                Diagnostic(ErrorCode.ERR_NameNotInContext, "b2").WithArguments("b2").WithLocation(38, 16),
                // (39,47): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //              Dummy(TakeOutParam(true, out var x9) && x9);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(39, 47),
                // (40,47): error CS0128: A local variable or function named 'x9' is already defined in this scope
                //              Dummy(TakeOutParam(true, out var x9) && x9))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x9").WithArguments("x9").WithLocation(40, 47));

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            AssertNotContainedInDeclaratorArguments(x4Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").Single();
            AssertNotContainedInDeclaratorArguments(x7Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x7Decl, x7Ref);

            var x8Decl = GetOutVarDeclarations(tree, "x8").ToArray();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(4, x8Decl.Length);
            Assert.Equal(4, x8Ref.Length);
            AssertNotContainedInDeclaratorArguments(x8Decl[0]);
            AssertNotContainedInDeclaratorArguments(x8Decl[1]);
            VerifyModelForOutVar(model, x8Decl[0], x8Ref[0]);
            VerifyModelForOutVar(model, x8Decl[1], x8Ref[1]);
            VerifyModelForOutVarWithoutDataFlow(model, x8Decl[2], isShadowed: true);
            VerifyModelForOutVarWithoutDataFlow(model, x8Decl[3], isShadowed: true);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(3, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            AssertNotContainedInDeclaratorArguments(x9Decl[0]);
            VerifyModelForOutVar(model, x9Decl[0], x9Ref[1]);
            VerifyModelForOutVar(model, x9Decl[1], x9Ref[2]);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[2], isShadowed: true);
        }

        [Fact]
        public void Scope_DeclaratorArguments_10()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (var d,e(Dummy(TakeOutParam(true, out var x1), x1)))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (var d,e(Dummy(TakeOutParam(true, out var x2), x2)))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        using (var d,e(Dummy(TakeOutParam(true, out var x4), x4)))
            Dummy(x4);
    }

    void Test6()
    {
        using (var d,e(Dummy(x6 && TakeOutParam(true, out var x6))))
            Dummy(x6);
    }

    void Test7()
    {
        using (var d,e(Dummy(TakeOutParam(true, out var x7) && x7)))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        using (var d,e(Dummy(TakeOutParam(true, out var x8), x8)))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        using (var d,a(Dummy(TakeOutParam(true, out var x9), x9)))
        {   
            Dummy(x9);
            using (var e,b(Dummy(TakeOutParam(true, out var x9), x9))) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        using (var d,e(Dummy(TakeOutParam(y10, out var x10), x10)))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    using (var d,e(Dummy(TakeOutParam(y11, out var x11), x11)))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        using (var d,e(Dummy(TakeOutParam(y12, out var x12), x12)))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    using (var d,e(Dummy(TakeOutParam(y13, out var x13), x13)))
    //        let y13 = 12;
    //}

    void Test14()
    {
        using (var d,e(Dummy(TakeOutParam(1, out var x14), 
                             TakeOutParam(2, out var x14), 
                             x14)))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.ERR_UnexpectedToken,
                                        (int)ErrorCode.WRN_UnreferencedVar,
                                        (int)ErrorCode.ERR_ImplicitlyTypedVariableMultipleDeclarator,
                                        (int)ErrorCode.ERR_FixedMustInit,
                                        (int)ErrorCode.ERR_ImplicitlyTypedVariableWithNoInitializer,
                                        (int)ErrorCode.ERR_UseDefViolation
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,57): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         using (var d,e(Dummy(TakeOutParam(true, out var x4), x4)))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 57),
                // (35,30): error CS0841: Cannot use local variable 'x6' before it is declared
                //         using (var d,e(Dummy(x6 && TakeOutParam(true, out var x6))))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 30),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,61): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             using (var e,b(Dummy(TakeOutParam(true, out var x9), x9))) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 61),
                // (68,43): error CS0103: The name 'y10' does not exist in the current context
                //         using (var d,e(Dummy(TakeOutParam(y10, out var x10), x10)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 43),
                // (86,43): error CS0103: The name 'y12' does not exist in the current context
                //         using (var d,e(Dummy(TakeOutParam(y12, out var x12), x12)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 43),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,54): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                              TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 54)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x2Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            AssertContainedInDeclaratorArguments(x6Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            AssertContainedInDeclaratorArguments(x7Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            AssertContainedInDeclaratorArguments(x8Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            AssertContainedInDeclaratorArguments(x9Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
            var x10Ref = GetReferences(tree, "x10").Single();
            AssertContainedInDeclaratorArguments(x10Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x10Decl, x10Ref);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            AssertContainedInDeclaratorArguments(x14Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_11()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (var d,x1(Dummy(TakeOutParam(true, out var x1), x1)))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (System.IDisposable d,x2(Dummy(TakeOutParam(true, out var x2), x2)))
        {
            Dummy(x2);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.WRN_UnreferencedVar,
                                        (int)ErrorCode.ERR_ImplicitlyTypedVariableMultipleDeclarator,
                                        (int)ErrorCode.ERR_FixedMustInit,
                                        (int)ErrorCode.ERR_ImplicitlyTypedVariableWithNoInitializer,
                                        (int)ErrorCode.ERR_UseDefViolation
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (12,58): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //         using (var d,x1(Dummy(TakeOutParam(true, out var x1), x1)))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(12, 58),
                // (20,73): error CS0128: A local variable or function named 'x2' is already defined in this scope
                //         using (System.IDisposable d,x2(Dummy(TakeOutParam(true, out var x2), x2)))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(20, 73)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            AssertContainedInDeclaratorArguments(x2Decl);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
            VerifyNotAnOutLocal(model, x2Ref[0]);
            VerifyNotAnOutLocal(model, x2Ref[1]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_12()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(params object[] x) {return null;}

    void Test1()
    {
        using (System.IDisposable d,e(Dummy(TakeOutParam(true, out var x1), x1)], 
                                  x1 = Dummy(x1))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (System.IDisposable d1,e(Dummy(TakeOutParam(true, out var x2), x2)], 
                                    d2(Dummy(TakeOutParam(true, out var x2), x2)))
        {
            Dummy(x2);
        }
    }

    void Test3()
    {
        using (System.IDisposable d1,e(Dummy(TakeOutParam(true, out var x3), x3)], 
                                  d2 = Dummy(x3))
        {
            Dummy(x3);
        }
    }

    void Test4()
    {
        using (System.IDisposable d1 = Dummy(x4), 
                                    d2(Dummy(TakeOutParam(true, out var x4), x4)))
        {
            Dummy(x4);
        }
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.ERR_UnexpectedToken,
                                        (int)ErrorCode.WRN_UnreferencedVar,
                                        (int)ErrorCode.ERR_FixedMustInit,
                                        (int)ErrorCode.ERR_UseDefViolation,
                                        (int)ErrorCode.ERR_CloseParenExpected
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (13,35): error CS0128: A local variable named 'x1' is already defined in this scope
                //                                   x1 = Dummy(x1))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 35),
                // (22,73): error CS0128: A local variable named 'x2' is already defined in this scope
                //                                     d2(Dummy(TakeOutParam(true, out var x2), x2)))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(22, 73),
                // (39,46): error CS0841: Cannot use local variable 'x4' before it is declared
                //         using (System.IDisposable d1 = Dummy(x4), 
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(39, 46)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(3, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x2Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl[0], x2Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x2Decl[1]);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(3, x3Ref.Length);
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref);
        }

        [Fact]
        public void Scope_DeclaratorArguments_13()
        {
            var source =
@"
public unsafe class X
{
    public static void Main()
    {
    }

    int[] Dummy(params object[] x) {return null;}

    void Test1()
    {
        fixed (int* p,e(Dummy(TakeOutParam(true, out var x1) && x1)))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        fixed (int* p,e(Dummy(TakeOutParam(true, out var x2) && x2)))
            Dummy(x2);
    }

    void Test4()
    {
        var x4 = 11;
        Dummy(x4);

        fixed (int* p,e(Dummy(TakeOutParam(true, out var x4) && x4)))
            Dummy(x4);
    }

    void Test6()
    {
        fixed (int* p,e(Dummy(x6 && TakeOutParam(true, out var x6))))
            Dummy(x6);
    }

    void Test7()
    {
        fixed (int* p,e(Dummy(TakeOutParam(true, out var x7) && x7)))
        {
            var x7 = 12;
            Dummy(x7);
        }
    }

    void Test8()
    {
        fixed (int* p,e(Dummy(TakeOutParam(true, out var x8) && x8)))
            Dummy(x8);

        System.Console.WriteLine(x8);
    }

    void Test9()
    {
        fixed (int* p1,a(Dummy(TakeOutParam(true, out var x9) && x9)))
        {   
            Dummy(x9);
            fixed (int* p2,b(Dummy(TakeOutParam(true, out var x9) && x9))) // 2
                Dummy(x9);
        }
    }

    void Test10()
    {
        fixed (int* p,e(Dummy(TakeOutParam(y10, out var x10))))
        {   
            var y10 = 12;
            Dummy(y10);
        }
    }

    //void Test11()
    //{
    //    fixed (int* p,e(Dummy(TakeOutParam(y11, out var x11))))
    //    {   
    //        let y11 = 12;
    //        Dummy(y11);
    //    }
    //}

    void Test12()
    {
        fixed (int* p,e(Dummy(TakeOutParam(y12, out var x12))))
            var y12 = 12;
    }

    //void Test13()
    //{
    //    fixed (int* p,e(Dummy(TakeOutParam(y13, out var x13))))
    //        let y13 = 12;
    //}

    void Test14()
    {
        fixed (int* p,e(Dummy(TakeOutParam(1, out var x14), 
                              TakeOutParam(2, out var x14), 
                              x14)))
        {
            Dummy(x14);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.ERR_UnexpectedToken,
                                        (int)ErrorCode.WRN_UnreferencedVar,
                                        (int)ErrorCode.ERR_FixedMustInit,
                                        (int)ErrorCode.ERR_UseDefViolation
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (87,13): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //             var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(87, 13),
                // (29,58): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         fixed (int* p,e(Dummy(TakeOutParam(true, out var x4) && x4)))
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(29, 58),
                // (35,31): error CS0841: Cannot use local variable 'x6' before it is declared
                //         fixed (int* p,e(Dummy(x6 && TakeOutParam(true, out var x6))))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(35, 31),
                // (43,17): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(43, 17),
                // (53,34): error CS0103: The name 'x8' does not exist in the current context
                //         System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(53, 34),
                // (61,63): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             fixed (int* p2,b(Dummy(TakeOutParam(true, out var x9) && x9))) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(61, 63),
                // (68,44): error CS0103: The name 'y10' does not exist in the current context
                //         fixed (int* p,e(Dummy(TakeOutParam(y10, out var x10))))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(68, 44),
                // (86,44): error CS0103: The name 'y12' does not exist in the current context
                //         fixed (int* p,e(Dummy(TakeOutParam(y12, out var x12))))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(86, 44),
                // (87,17): warning CS0219: The variable 'y12' is assigned but its value is never used
                //             var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(87, 17),
                // (99,55): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                               TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(99, 55)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x2Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl, x2Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(3, x4Ref.Length);
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyNotAnOutLocal(model, x4Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl, x4Ref[1], x4Ref[2]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Ref.Length);
            AssertContainedInDeclaratorArguments(x6Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x6Decl, x6Ref);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(2, x7Ref.Length);
            AssertContainedInDeclaratorArguments(x7Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x7Decl, x7Ref[0]);
            VerifyNotAnOutLocal(model, x7Ref[1]);

            var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
            var x8Ref = GetReferences(tree, "x8").ToArray();
            Assert.Equal(3, x8Ref.Length);
            AssertContainedInDeclaratorArguments(x8Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x8Decl, x8Ref[0], x8Ref[1]);
            VerifyNotInScope(model, x8Ref[2]);

            var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
            var x9Ref = GetReferences(tree, "x9").ToArray();
            Assert.Equal(2, x9Decl.Length);
            Assert.Equal(4, x9Ref.Length);
            AssertContainedInDeclaratorArguments(x9Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[0], x9Ref[0], x9Ref[1]);
            VerifyModelForOutVarWithoutDataFlow(model, x9Decl[1], x9Ref[2], x9Ref[3]);

            var y10Ref = GetReferences(tree, "y10").ToArray();
            Assert.Equal(2, y10Ref.Length);
            VerifyNotInScope(model, y10Ref[0]);
            VerifyNotAnOutLocal(model, y10Ref[1]);

            var y12Ref = GetReferences(tree, "y12").Single();
            VerifyNotInScope(model, y12Ref);

            var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
            var x14Ref = GetReferences(tree, "x14").ToArray();
            Assert.Equal(2, x14Decl.Length);
            Assert.Equal(2, x14Ref.Length);
            AssertContainedInDeclaratorArguments(x14Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x14Decl[0], x14Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_14()
        {
            var source =
@"
public unsafe class X
{
    public static void Main()
    {
    }

    int[] Dummy(params object[] x) {return null;}
    int[] Dummy(int* x) {return null;}

    void Test1()
    {
        fixed (int* d,x1( 
                         Dummy(TakeOutParam(true, out var x1) && x1)))
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        fixed (int* d,p(Dummy(TakeOutParam(true, out var x2) && x2)],
                    x2 = Dummy())
        {
            Dummy(x2);
        }
    }

    void Test3()
    {
        fixed (int* x3 = Dummy(),
                      p(Dummy(TakeOutParam(true, out var x3) && x3)))
        {
            Dummy(x3);
        }
    }

    void Test4()
    {
        fixed (int* d,p1(Dummy(TakeOutParam(true, out var x4) && x4)],
                      p2(Dummy(TakeOutParam(true, out var x4) && x4)))
        {
            Dummy(x4);
        }
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                        (int)ErrorCode.ERR_SyntaxError,
                                        (int)ErrorCode.ERR_UnexpectedToken,
                                        (int)ErrorCode.WRN_UnreferencedVar,
                                        (int)ErrorCode.ERR_FixedMustInit,
                                        (int)ErrorCode.ERR_UseDefViolation,
                                        (int)ErrorCode.ERR_CloseParenExpected
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (14,59): error CS0128: A local variable named 'x1' is already defined in this scope
                //                          Dummy(TakeOutParam(true, out var x1) && x1)))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(14, 59),
                // (14,32): error CS0019: Operator '&&' cannot be applied to operands of type 'bool' and 'int*'
                //                          Dummy(TakeOutParam(true, out var x1) && x1)))
                Diagnostic(ErrorCode.ERR_BadBinaryOps, "TakeOutParam(true, out var x1) && x1").WithArguments("&&", "bool", "int*").WithLocation(14, 32),
                // (23,21): error CS0128: A local variable named 'x2' is already defined in this scope
                //                     x2 = Dummy())
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(23, 21),
                // (32,58): error CS0128: A local variable named 'x3' is already defined in this scope
                //                       p(Dummy(TakeOutParam(true, out var x3) && x3)))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(32, 58),
                // (32,31): error CS0019: Operator '&&' cannot be applied to operands of type 'bool' and 'int*'
                //                       p(Dummy(TakeOutParam(true, out var x3) && x3)))
                Diagnostic(ErrorCode.ERR_BadBinaryOps, "TakeOutParam(true, out var x3) && x3").WithArguments("&&", "bool", "int*").WithLocation(32, 31),
                // (41,59): error CS0128: A local variable named 'x4' is already defined in this scope
                //                       p2(Dummy(TakeOutParam(true, out var x4) && x4)))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(41, 59)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            AssertContainedInDeclaratorArguments(x1Decl);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);
            VerifyNotAnOutLocal(model, x1Ref[0]);
            VerifyNotAnOutLocal(model, x1Ref[1]);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            AssertContainedInDeclaratorArguments(x2Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(2, x3Ref.Length);
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelForOutVarDuplicateInSameScope(model, x3Decl);
            VerifyNotAnOutLocal(model, x3Ref[0]);
            VerifyNotAnOutLocal(model, x3Ref[1]);

            var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
            var x4Ref = GetReferences(tree, "x4").ToArray();
            Assert.Equal(2, x4Decl.Length);
            Assert.Equal(3, x4Ref.Length);
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelForOutVarWithoutDataFlow(model, x4Decl[0], x4Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_15()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Test3  [TakeOutParam(3, out var x3) && x3 > 0];

    bool Test4  [x4 && TakeOutParam(4, out var x4)];

    bool Test5  [TakeOutParam(51, out var x5) && 
                 TakeOutParam(52, out var x5) && 
                 x5 > 0];

    bool Test61  [TakeOutParam(6, out var x6) && x6 > 0], Test62 [TakeOutParam(6, out var x6) && x6 > 0];

    bool Test71  [TakeOutParam(7, out var x7) && x7 > 0]; 
    bool Test72  [Dummy(x7, 2)]; 
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_CStyleArray,
                                        (int)ErrorCode.ERR_ArraySizeInDeclaration,
                                        (int)ErrorCode.WRN_UnreferencedField
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (20,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(20, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelNotSupported(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelNotSupported(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            AssertContainedInDeclaratorArguments(x5Decl);
            VerifyModelNotSupported(model, x5Decl[0], x5Ref);
            VerifyModelNotSupported(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            AssertContainedInDeclaratorArguments(x6Decl);
            VerifyModelNotSupported(model, x6Decl[0], x6Ref[0]);
            VerifyModelNotSupported(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            AssertContainedInDeclaratorArguments(x7Decl);
            VerifyModelNotSupported(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        private static void VerifyModelNotSupported(
            SemanticModel model,
            DeclarationExpressionSyntax decl,
            params IdentifierNameSyntax[] references)
        {
            var variableDeclaratorSyntax = GetVariableDesignation(decl);
            Assert.Null(model.GetDeclaredSymbol(variableDeclaratorSyntax));
            Assert.Null(model.GetDeclaredSymbol((SyntaxNode)variableDeclaratorSyntax));
            var identifierText = decl.Identifier().ValueText;
            Assert.False(model.LookupSymbols(decl.SpanStart, name: identifierText).Any());

            Assert.False(model.LookupNames(decl.SpanStart).Contains(identifierText));
            Assert.Null(model.GetSymbolInfo(decl.Type).Symbol);

            AssertInfoForDeclarationExpressionSyntax(model, decl, expectedSymbol: null, expectedType: null);

            VerifyModelNotSupported(model, references);
        }

        private static void VerifyModelNotSupported(SemanticModel model, params IdentifierNameSyntax[] references)
        {
            foreach (var reference in references)
            {
                Assert.Null(model.GetSymbolInfo(reference).Symbol);
                Assert.False(model.LookupSymbols(reference.SpanStart, name: reference.Identifier.ValueText).Any());
                Assert.DoesNotContain(reference.Identifier.ValueText, model.LookupNames(reference.SpanStart));
                Assert.True(((ITypeSymbol)model.GetTypeInfo(reference).Type).IsErrorType());
            }
        }

        [Fact]
        public void Scope_DeclaratorArguments_16()
        {
            var source =
@"
public unsafe struct X
{
    public static void Main()
    {
    }
    fixed
    bool Test3  [TakeOutParam(3, out var x3) && x3 > 0];
    fixed
    bool Test4  [x4 && TakeOutParam(4, out var x4)];
    fixed
    bool Test5  [TakeOutParam(51, out var x5) && 
                 TakeOutParam(52, out var x5) && 
                 x5 > 0];
    fixed
    bool Test61  [TakeOutParam(6, out var x6) && x6 > 0], Test62 [TakeOutParam(6, out var x6) && x6 > 0];
    fixed
    bool Test71  [TakeOutParam(7, out var x7) && x7 > 0]; 
    fixed
    bool Test72  [Dummy(x7, 2)]; 
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_CStyleArray,
                                        (int)ErrorCode.ERR_ArraySizeInDeclaration,
                                        (int)ErrorCode.WRN_UnreferencedField,
                                        (int)ErrorCode.ERR_NoImplicitConv
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (10,18): error CS0841: Cannot use local variable 'x4' before it is declared
                //     bool Test4  [x4 && TakeOutParam(4, out var x4)];
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(10, 18),
                // (13,43): error CS0128: A local variable named 'x5' is already defined in this scope
                //                  TakeOutParam(52, out var x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(13, 43),
                // (20,25): error CS0103: The name 'x7' does not exist in the current context
                //     bool Test72  [Dummy(x7, 2)]; 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(20, 25),
                // (21,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(21, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelNotSupported(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelNotSupported(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            AssertContainedInDeclaratorArguments(x5Decl);
            VerifyModelNotSupported(model, x5Decl[0], x5Ref);
            VerifyModelNotSupported(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            AssertContainedInDeclaratorArguments(x6Decl);
            VerifyModelNotSupported(model, x6Decl[0], x6Ref[0]);
            VerifyModelNotSupported(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            AssertContainedInDeclaratorArguments(x7Decl);
            VerifyModelNotSupported(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_17()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }
    const
    bool Test3  [TakeOutParam(3, out var x3) && x3 > 0];
    const
    bool Test4  [x4 && TakeOutParam(4, out var x4)];
    const
    bool Test5  [TakeOutParam(51, out var x5) && 
                 TakeOutParam(52, out var x5) && 
                 x5 > 0];
    const
    bool Test61  [TakeOutParam(6, out var x6) && x6 > 0], Test62 [TakeOutParam(6, out var x6) && x6 > 0];
    const
    bool Test71  [TakeOutParam(7, out var x7) && x7 > 0]; 
    const
    bool Test72  [Dummy(x7, 2)]; 
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_CStyleArray,
                                        (int)ErrorCode.ERR_ArraySizeInDeclaration
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (21,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(21, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelNotSupported(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelNotSupported(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            AssertContainedInDeclaratorArguments(x5Decl);
            VerifyModelNotSupported(model, x5Decl[0], x5Ref);
            VerifyModelNotSupported(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            AssertContainedInDeclaratorArguments(x6Decl);
            VerifyModelNotSupported(model, x6Decl[0], x6Ref[0]);
            VerifyModelNotSupported(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            AssertContainedInDeclaratorArguments(x7Decl);
            VerifyModelNotSupported(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_18()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }
    event
    bool Test3  [TakeOutParam(3, out var x3) && x3 > 0];
    event
    bool Test4  [x4 && TakeOutParam(4, out var x4)];
    event
    bool Test5  [TakeOutParam(51, out var x5) && 
                 TakeOutParam(52, out var x5) && 
                 x5 > 0];
    event
    bool Test61  [TakeOutParam(6, out var x6) && x6 > 0], Test62 [TakeOutParam(6, out var x6) && x6 > 0];
    event
    bool Test71  [TakeOutParam(7, out var x7) && x7 > 0]; 
    event
    bool Test72  [Dummy(x7, 2)]; 
    void Test73() { Dummy(x7, 3); } 

    bool Dummy(params object[] x) {return true;}
    static bool TakeOutParam(object y, out int x) 
    {
        x = 123;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_CStyleArray,
                                        (int)ErrorCode.ERR_ArraySizeInDeclaration,
                                        (int)ErrorCode.ERR_EventNotDelegate,
                                        (int)ErrorCode.WRN_UnreferencedEvent
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (21,27): error CS0103: The name 'x7' does not exist in the current context
                //     void Test73() { Dummy(x7, 3); } 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(21, 27)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").Single();
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelNotSupported(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
            var x4Ref = GetReferences(tree, "x4").Single();
            AssertContainedInDeclaratorArguments(x4Decl);
            VerifyModelNotSupported(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReferences(tree, "x5").Single();
            Assert.Equal(2, x5Decl.Length);
            AssertContainedInDeclaratorArguments(x5Decl);
            VerifyModelNotSupported(model, x5Decl[0], x5Ref);
            VerifyModelNotSupported(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            AssertContainedInDeclaratorArguments(x6Decl);
            VerifyModelNotSupported(model, x6Decl[0], x6Ref[0]);
            VerifyModelNotSupported(model, x6Decl[1], x6Ref[1]);

            var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            AssertContainedInDeclaratorArguments(x7Decl);
            VerifyModelNotSupported(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_DeclaratorArguments_19()
        {
            var source =
@"
public unsafe struct X
{
    public static void Main()
    {
    }

    fixed bool d[2], Test3 (out var x3);
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);
            int[] exclude = new int[] { (int)ErrorCode.ERR_BadVarDecl,
                                      };

            compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                // (8,28): error CS1003: Syntax error, '[' expected
                //     fixed bool d[2], Test3 (out var x3);
                Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(8, 28),
                // (8,39): error CS1003: Syntax error, ']' expected
                //     fixed bool d[2], Test3 (out var x3);
                Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(8, 39),
                // (8,33): error CS8185: A declaration is not allowed in this context.
                //     fixed bool d[2], Test3 (out var x3);
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "var x3").WithLocation(8, 33)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            AssertContainedInDeclaratorArguments(x3Decl);
            VerifyModelNotSupported(model, x3Decl);
        }

        [Fact]
        public void Scope_DeclaratorArguments_20()
        {
            var source =
@"
public unsafe struct X
{
    public static void Main()
    {
    }

    fixed bool Test3[out var x3];
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithAllowUnsafe(true), parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (8,22): error CS1003: Syntax error, ',' expected
                //     fixed bool Test3[out var x3];
                Diagnostic(ErrorCode.ERR_SyntaxError, "out").WithArguments(",").WithLocation(8, 22),
                // (8,30): error CS1003: Syntax error, ',' expected
                //     fixed bool Test3[out var x3];
                Diagnostic(ErrorCode.ERR_SyntaxError, "x3").WithArguments(",").WithLocation(8, 30),
                // (8,21): error CS7092: A fixed buffer may only have one dimension.
                //     fixed bool Test3[out var x3];
                Diagnostic(ErrorCode.ERR_FixedBufferTooManyDimensions, "[out var x3]").WithLocation(8, 21),
                // (8,26): error CS0103: The name 'var' does not exist in the current context
                //     fixed bool Test3[out var x3];
                Diagnostic(ErrorCode.ERR_NameNotInContext, "var").WithArguments("var").WithLocation(8, 26)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            Assert.False(GetOutVarDeclarations(tree, "x3").Any());
        }

        [Fact]
        public void StaticType()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        Test1(out StaticType x1);
    }

    static object Test1(out StaticType x)
    {
        throw new System.NotSupportedException();
    }

    static class StaticType {}
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (9,29): error CS0721: 'Cls.StaticType': static types cannot be used as parameters
                //     static object Test1(out StaticType x)
                Diagnostic(ErrorCode.ERR_ParameterIsStaticClass, "StaticType").WithArguments("Cls.StaticType").WithLocation(9, 29),
                // (6,19): error CS0723: Cannot declare a variable of static type 'Cls.StaticType'
                //         Test1(out StaticType x1);
                Diagnostic(ErrorCode.ERR_VarDeclIsStaticClass, "StaticType").WithArguments("Cls.StaticType").WithLocation(6, 19)
                );
        }

        [Fact]
        public void GlobalCode_Catch_01()
        {
            var source =
@"
bool Dummy(params object[] x) {return true;}

try {}
catch when (TakeOutParam(out var x1) && x1 > 0)
{
    Dummy(x1);
}

var x4 = 11;
Dummy(x4);

try {}
catch when (TakeOutParam(out var x4) && x4 > 0)
{
    Dummy(x4);
}

try {}
catch when (x6 && TakeOutParam(out var x6))
{
    Dummy(x6);
}

try {}
catch when (TakeOutParam(out var x7) && x7 > 0)
{
    var x7 = 12;
    Dummy(x7);
}

try {}
catch when (TakeOutParam(out var x8) && x8 > 0)
{
    Dummy(x8);
}

System.Console.WriteLine(x8);

try {}
catch when (TakeOutParam(out var x9) && x9 > 0)
{   
    Dummy(x9);
    try {}
    catch when (TakeOutParam(out var x9) && x9 > 0) // 2
    {
        Dummy(x9);
    }
}

try {}
catch when (TakeOutParam(y10, out var x10))
{   
    var y10 = 12;
    Dummy(y10);
}

//    try {}
//    catch when (TakeOutParam(y11, out var x11)
//    {   
//        let y11 = 12;
//        Dummy(y11);
//    }

try {}
catch when (Dummy(TakeOutParam(out var x14), 
                    TakeOutParam(out var x14), // 2
                    x14))
{
    Dummy(x14);
}

try {}
catch (System.Exception x15)
        when (Dummy(TakeOutParam(out var x15), x15))
{
    Dummy(x15);
}

static bool TakeOutParam(out int x) 
{
    x = 123;
    return true;
}
static bool TakeOutParam(object y, out int x)
{
    x = 123;
    return true;
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
                compilation.VerifyDiagnostics(
                // (20,13): error CS0841: Cannot use local variable 'x6' before it is declared
                // catch when (x6 && TakeOutParam(out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(20, 13),
                // (28,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(28, 9),
                // (38,26): error CS0103: The name 'x8' does not exist in the current context
                // System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(38, 26),
                // (45,38): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     catch when (TakeOutParam(out var x9) && x9 > 0) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(45, 38),
                // (52,26): error CS0103: The name 'y10' does not exist in the current context
                // catch when (TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(52, 26),
                // (67,42): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                     TakeOutParam(out var x14), // 2
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(67, 42),
                // (75,42): error CS0128: A local variable or function named 'x15' is already defined in this scope
                //         when (Dummy(TakeOutParam(out var x15), x15))
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x15").WithArguments("x15").WithLocation(75, 42)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclaration(tree, "x1");
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x4Decl = GetOutVarDeclaration(tree, "x4");
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclaration(tree, "x6");
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclaration(tree, "x7");
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclaration(tree, "x8");
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

                var x15Decl = GetOutVarDeclaration(tree, "x15");
                var x15Ref = GetReferences(tree, "x15").ToArray();
                Assert.Equal(2, x15Ref.Length);
                VerifyModelForOutVarDuplicateInSameScope(model, x15Decl);
                VerifyNotAnOutLocal(model, x15Ref[0]);
                VerifyNotAnOutLocal(model, x15Ref[1]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (14,34): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // catch when (TakeOutParam(out var x4) && x4 > 0)
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(14, 34),
                    // (20,13): error CS0841: Cannot use local variable 'x6' before it is declared
                    // catch when (x6 && TakeOutParam(out var x6))
                    Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(20, 13),
                    // (28,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     var x7 = 12;
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(28, 9),
                    // (38,26): error CS0103: The name 'x8' does not exist in the current context
                    // System.Console.WriteLine(x8);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(38, 26),
                    // (45,38): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     catch when (TakeOutParam(out var x9) && x9 > 0) // 2
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(45, 38),
                    // (52,26): error CS0103: The name 'y10' does not exist in the current context
                    // catch when (TakeOutParam(y10, out var x10))
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(52, 26),
                    // (67,42): error CS0128: A local variable or function named 'x14' is already defined in this scope
                    //                     TakeOutParam(out var x14), // 2
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(67, 42),
                    // (75,42): error CS0128: A local variable or function named 'x15' is already defined in this scope
                    //         when (Dummy(TakeOutParam(out var x15), x15))
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x15").WithArguments("x15").WithLocation(75, 42),
                    // (85,13): error CS0128: A local variable or function named 'TakeOutParam' is already defined in this scope
                    // static bool TakeOutParam(object y, out int x)
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "TakeOutParam").WithArguments("TakeOutParam").WithLocation(85, 13),
                    // (85,13): warning CS8321: The local function 'TakeOutParam' is declared but never used
                    // static bool TakeOutParam(object y, out int x)
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "TakeOutParam").WithArguments("TakeOutParam").WithLocation(85, 13)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclaration(tree, "x1");
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x4Decl = GetOutVarDeclaration(tree, "x4");
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclaration(tree, "x6");
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclaration(tree, "x7");
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclaration(tree, "x8");
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

                var x15Decl = GetOutVarDeclaration(tree, "x15");
                var x15Ref = GetReferences(tree, "x15").ToArray();
                Assert.Equal(2, x15Ref.Length);
                VerifyModelForOutVarDuplicateInSameScope(model, x15Decl);
                VerifyNotAnOutLocal(model, x15Ref[0]);
                VerifyNotAnOutLocal(model, x15Ref[1]);
            }
        }

        [Fact]
        public void GlobalCode_Catch_02()
        {
            var source =
@"
try
{
    throw new System.InvalidOperationException();
}
catch (System.Exception e) when (Dummy(TakeOutParam(e, out var x1), x1))
{
    System.Console.WriteLine(x1.GetType());
}

static bool Dummy(object y, object z) 
{
    System.Console.WriteLine(z.GetType());
    return true;
}

static bool TakeOutParam<T>(T y, out T x) 
{
    x = y;
    return true;
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
            CompileAndVerify(compilation, expectedOutput:
@"System.InvalidOperationException
System.InvalidOperationException");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_Block_01()
        {
            string source =
@"
{
    H.TakeOutParam(1, out var x1);
    H.Dummy(x1);
}

object x2;
{
    H.TakeOutParam(2, out var x2);
    H.Dummy(x2);
}
{
    H.TakeOutParam(3, out var x3);
}
H.Dummy(x3);

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (15,9): error CS0103: The name 'x3' does not exist in the current context
                // H.Dummy(x3);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x3").WithArguments("x3").WithLocation(15, 9)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(1, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotInScope(model, x3Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (7,8): warning CS0168: The variable 'x2' is declared but never used
                    // object x2;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x2").WithArguments("x2").WithLocation(7, 8),
                    // (9,31): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(9, 31),
                    // (15,9): error CS0103: The name 'x3' does not exist in the current context
                    // H.Dummy(x3);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x3").WithArguments("x3").WithLocation(15, 9)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(1, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotInScope(model, x3Ref);
            }
        }

        [Fact]
        public void GlobalCode_Block_02()
        {
            string source =
@"
{
    H.TakeOutParam(1, out var x1);
    System.Console.WriteLine(x1);
    Test();

    void Test()
    {
        System.Console.WriteLine(x1);
    }
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"1
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_For_01()
        {
            var source =
@"
bool Dummy(params object[] x) {return true;}

for (
        Dummy(TakeOutParam(true, out var x1) && x1)
        ;;)
{
    Dummy(x1);
}

for ( // 2
        Dummy(TakeOutParam(true, out var x2) && x2)
        ;;)
    Dummy(x2);

var x4 = 11;
Dummy(x4);

for (
        Dummy(TakeOutParam(true, out var x4) && x4)
        ;;)
    Dummy(x4);

for (
        Dummy(x6 && TakeOutParam(true, out var x6))
        ;;)
    Dummy(x6);

for (
        Dummy(TakeOutParam(true, out var x7) && x7)
        ;;)
{
    var x7 = 12;
    Dummy(x7);
}

for (
        Dummy(TakeOutParam(true, out var x8) && x8)
        ;;)
    Dummy(x8);

System.Console.WriteLine(x8);

for (
        Dummy(TakeOutParam(true, out var x9) && x9)
        ;;)
{   
    Dummy(x9);
    for (
            Dummy(TakeOutParam(true, out var x9) && x9) // 2
            ;;)
        Dummy(x9);
}

for (
        Dummy(TakeOutParam(y10, out var x10))
        ;;)
{   
    var y10 = 12;
    Dummy(y10);
}

//    for (
//         Dummy(TakeOutParam(y11, out var x11))
//         ;;)
//    {   
//        let y11 = 12;
//        Dummy(y11);
//    }

for (
        Dummy(TakeOutParam(y12, out var x12))
        ;;)
    var y12 = 12;

//    for (
//         Dummy(TakeOutParam(y13, out var x13))
//         ;;)
//        let y13 = 12;

for (
        Dummy(TakeOutParam(1, out var x14), 
            TakeOutParam(2, out var x14), 
            x14)
        ;;)
{
    Dummy(x14);
}

static bool TakeOutParam(object y, out bool x) 
{
    x = true;
    return true;
}
";

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
                compilation.VerifyDiagnostics(
                // (74,5): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //     var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(74, 5),
                // (25,15): error CS0841: Cannot use local variable 'x6' before it is declared
                //         Dummy(x6 && TakeOutParam(true, out var x6))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(25, 15),
                // (33,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(33, 9),
                // (42,26): error CS0103: The name 'x8' does not exist in the current context
                // System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(42, 26),
                // (50,46): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             Dummy(TakeOutParam(true, out var x9) && x9) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(50, 46),
                // (56,28): error CS0103: The name 'y10' does not exist in the current context
                //         Dummy(TakeOutParam(y10, out var x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(56, 28),
                // (72,28): error CS0103: The name 'y12' does not exist in the current context
                //         Dummy(TakeOutParam(y12, out var x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(72, 28),
                // (83,37): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //             TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(83, 37),
                // (11,1): warning CS0162: Unreachable code detected
                // for ( // 2
                Diagnostic(ErrorCode.WRN_UnreachableCode, "for").WithLocation(11, 1),
                // (74,9): warning CS0219: The variable 'y12' is assigned but its value is never used
                //     var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(74, 9)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").ToArray();
                Assert.Equal(2, x2Ref.Length);
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var y12Ref = GetReferences(tree, "y12").Single();
                VerifyNotInScope(model, y12Ref);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (20,42): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //         Dummy(TakeOutParam(true, out var x4) && x4)
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(20, 42),
                    // (74,5): error CS1023: Embedded statement cannot be a declaration or labeled statement
                    //     var y12 = 12;
                    Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(74, 5),
                    // (25,15): error CS0841: Cannot use local variable 'x6' before it is declared
                    //         Dummy(x6 && TakeOutParam(true, out var x6))
                    Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(25, 15),
                    // (33,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     var x7 = 12;
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(33, 9),
                    // (42,26): error CS0103: The name 'x8' does not exist in the current context
                    // System.Console.WriteLine(x8);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(42, 26),
                    // (50,46): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //             Dummy(TakeOutParam(true, out var x9) && x9) // 2
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(50, 46),
                    // (56,28): error CS0103: The name 'y10' does not exist in the current context
                    //         Dummy(TakeOutParam(y10, out var x10))
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(56, 28),
                    // (72,28): error CS0103: The name 'y12' does not exist in the current context
                    //         Dummy(TakeOutParam(y12, out var x12))
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(72, 28),
                    // (83,37): error CS0128: A local variable or function named 'x14' is already defined in this scope
                    //             TakeOutParam(2, out var x14), 
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(83, 37),
                    // (11,1): warning CS0162: Unreachable code detected
                    // for ( // 2
                    Diagnostic(ErrorCode.WRN_UnreachableCode, "for").WithLocation(11, 1),
                    // (74,9): warning CS0219: The variable 'y12' is assigned but its value is never used
                    //     var y12 = 12;
                    Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(74, 9)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").ToArray();
                Assert.Equal(2, x2Ref.Length);
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var y12Ref = GetReferences(tree, "y12").Single();
                VerifyNotInScope(model, y12Ref);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_For_02()
        {
            var source =
@"
bool f = true;

for (Dummy(f, TakeOutParam((f ? 10 : 20), out var x0), x0); 
        Dummy(f, TakeOutParam((f ? 1 : 2), out var x1), x1); 
        Dummy(f, TakeOutParam((f ? 100 : 200), out var x2), x2), Dummy(true, null, x2))
{
    System.Console.WriteLine(x0);
    System.Console.WriteLine(x1);
    f = false;
}

static bool Dummy(bool x, object y, object z) 
{
    System.Console.WriteLine(z);
    return x;
}

static bool TakeOutParam(int y, out int x) 
{
    x = y;
    return true;
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
            CompileAndVerify(compilation, expectedOutput:
@"10
1
10
1
200
200
2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x0Decl = GetOutVarDeclarations(tree, "x0").Single();
            var x0Ref = GetReferences(tree, "x0").ToArray();
            Assert.Equal(2, x0Ref.Length);
            VerifyModelForOutVar(model, x0Decl, x0Ref);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl, x2Ref);
        }

        [Fact]
        public void GlobalCode_Foreach_01()
        {
            var source =
@"using static Helpers;
System.Collections.IEnumerable Dummy(params object[] x) {return null;}

foreach (var i in Dummy(TakeOutParam(true, out var x1) && x1))
{
    Dummy(x1);
}

foreach (var i in Dummy(TakeOutParam(true, out var x2) && x2))
    Dummy(x2);

var x4 = 11;
Dummy(x4);

foreach (var i in Dummy(TakeOutParam(true, out var x4) && x4))
    Dummy(x4);

foreach (var i in Dummy(x6 && TakeOutParam(true, out var x6)))
    Dummy(x6);

foreach (var i in Dummy(TakeOutParam(true, out var x7) && x7))
{
    var x7 = 12;
    Dummy(x7);
}

foreach (var i in Dummy(TakeOutParam(true, out var x8) && x8))
    Dummy(x8);

System.Console.WriteLine(x8);

foreach (var i1 in Dummy(TakeOutParam(true, out var x9) && x9))
{   
    Dummy(x9);
    foreach (var i2 in Dummy(TakeOutParam(true, out var x9) && x9)) // 2
        Dummy(x9);
}

foreach (var i in Dummy(TakeOutParam(y10, out var x10)))
{   
    var y10 = 12;
    Dummy(y10);
}

//    foreach (var i in Dummy(TakeOutParam(y11, out var x11)))
//    {   
//        let y11 = 12;
//        Dummy(y11);
//    }

foreach (var i in Dummy(TakeOutParam(y12, out var x12)))
    var y12 = 12;

//    foreach (var i in Dummy(TakeOutParam(y13, out var x13)))
//        let y13 = 12;

foreach (var i in Dummy(TakeOutParam(1, out var x14), 
                        TakeOutParam(2, out var x14), 
                        x14))
{
    Dummy(x14);
}

foreach (var x15 in 
                    Dummy(TakeOutParam(1, out var x15), x15))
{
    Dummy(x15);
}

static class Helpers
{
    public static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }

    public static bool TakeOutParam(bool y, out bool x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
                compilation.VerifyDiagnostics(
                // (52,5): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //     var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(52, 5),
                // (18,25): error CS0841: Cannot use local variable 'x6' before it is declared
                // foreach (var i in Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(18, 25),
                // (23,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(23, 9),
                // (30,26): error CS0103: The name 'x8' does not exist in the current context
                // System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(30, 26),
                // (35,57): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     foreach (var i2 in Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(35, 57),
                // (39,38): error CS0103: The name 'y10' does not exist in the current context
                // foreach (var i in Dummy(TakeOutParam(y10, out var x10)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(39, 38),
                // (51,38): error CS0103: The name 'y12' does not exist in the current context
                // foreach (var i in Dummy(TakeOutParam(y12, out var x12)))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(51, 38),
                // (58,49): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                         TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(58, 49),
                // (64,14): error CS0136: A local or parameter named 'x15' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                // foreach (var x15 in 
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x15").WithArguments("x15").WithLocation(64, 14),
                // (52,9): warning CS0219: The variable 'y12' is assigned but its value is never used
                //     var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(52, 9)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").ToArray();
                Assert.Equal(2, x2Ref.Length);
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var y12Ref = GetReferences(tree, "y12").Single();
                VerifyNotInScope(model, y12Ref);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

                var x15Decl = GetOutVarDeclarations(tree, "x15").Single();
                var x15Ref = GetReferences(tree, "x15").ToArray();
                Assert.Equal(2, x15Ref.Length);
                VerifyModelForOutVar(model, x15Decl, x15Ref[0]);
                VerifyNotAnOutLocal(model, x15Ref[1]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (15,52): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // foreach (var i in Dummy(TakeOutParam(true, out var x4) && x4))
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(15, 52),
                    // (52,5): error CS1023: Embedded statement cannot be a declaration or labeled statement
                    //     var y12 = 12;
                    Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(52, 5),
                    // (18,25): error CS0841: Cannot use local variable 'x6' before it is declared
                    // foreach (var i in Dummy(x6 && TakeOutParam(true, out var x6)))
                    Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(18, 25),
                    // (23,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     var x7 = 12;
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(23, 9),
                    // (30,26): error CS0103: The name 'x8' does not exist in the current context
                    // System.Console.WriteLine(x8);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(30, 26),
                    // (35,57): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     foreach (var i2 in Dummy(TakeOutParam(true, out var x9) && x9)) // 2
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(35, 57),
                    // (39,38): error CS0103: The name 'y10' does not exist in the current context
                    // foreach (var i in Dummy(TakeOutParam(y10, out var x10)))
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(39, 38),
                    // (51,38): error CS0103: The name 'y12' does not exist in the current context
                    // foreach (var i in Dummy(TakeOutParam(y12, out var x12)))
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(51, 38),
                    // (58,49): error CS0128: A local variable or function named 'x14' is already defined in this scope
                    //                         TakeOutParam(2, out var x14), 
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(58, 49),
                    // (64,14): error CS0136: A local or parameter named 'x15' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // foreach (var x15 in 
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x15").WithArguments("x15").WithLocation(64, 14),
                    // (52,9): warning CS0219: The variable 'y12' is assigned but its value is never used
                    //     var y12 = 12;
                    Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(52, 9)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").ToArray();
                Assert.Equal(2, x2Ref.Length);
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var y12Ref = GetReferences(tree, "y12").Single();
                VerifyNotInScope(model, y12Ref);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);

                var x15Decl = GetOutVarDeclarations(tree, "x15").Single();
                var x15Ref = GetReferences(tree, "x15").ToArray();
                Assert.Equal(2, x15Ref.Length);
                VerifyModelForOutVar(model, x15Decl, x15Ref[0]);
                VerifyNotAnOutLocal(model, x15Ref[1]);
            }
        }

        [Fact]
        public void GlobalCode_Foreach_02()
        {
            var source =
@"
bool f = true;

foreach (var i in Dummy(TakeOutParam(3, out var x1), x1))
{
    System.Console.WriteLine(x1);
}

static System.Collections.IEnumerable Dummy(object y, object z) 
{
    System.Console.WriteLine(z);
    return ""a"";
}

static bool TakeOutParam(int y, out int x) 
{
    x = y;
    return true;
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
            CompileAndVerify(compilation, expectedOutput:
@"3
3");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_Lambda_01()
        {
            var source =
@"
bool Dummy(params object[] x) {return true;}

Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out var x3) && x3 > 0));

Dummy((System.Func<object, bool>) (o => x4 && TakeOutParam(o, out var x4)));

Dummy((System.Func<object, object, bool>) ((o1, o2) => TakeOutParam(o1, out var x5) && 
                                                        TakeOutParam(o2, out var x5) && 
                                                        x5 > 0));

Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out var x6) && x6 > 0), (System.Func<object, bool>) (o => TakeOutParam(o, out var x6) && x6 > 0));

Dummy(x7, 1);
Dummy(x7, 
        (System.Func<object, bool>) (o => TakeOutParam(o, out var x7) && x7 > 0), 
        x7);
Dummy(x7, 2); 

Dummy(TakeOutParam(true, out var x8) && x8, (System.Func<object, bool>) (o => TakeOutParam(o, out var y8) && x8));

Dummy(TakeOutParam(true, out var x9), 
        (System.Func<object, bool>) (o => TakeOutParam(o, out var x9) && 
                                        x9 > 0), x9);

Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out var x10) && 
                                        x10 > 0),
        TakeOutParam(true, out var x10), x10);

var x11 = 11;
Dummy(x11);
Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out var x11) && 
                                        x11 > 0), x11);

Dummy((System.Func<object, bool>) (o => TakeOutParam(o, out var x12) && 
                                        x12 > 0), 
        x12);
var x12 = 11;
Dummy(x12);

static bool TakeOutParam(object y, out int x) 
{
    x = 123;
    return true;
}

static bool TakeOutParam(bool y, out bool x) 
{
    x = true;
    return true;
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
                compilation.VerifyDiagnostics(
                // (6,41): error CS0841: Cannot use local variable 'x4' before it is declared
                // Dummy((System.Func<object, bool>) (o => x4 && TakeOutParam(o, out var x4)));
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(6, 41),
                // (9,82): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                                                         TakeOutParam(o2, out var x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(9, 82),
                // (14,7): error CS0103: The name 'x7' does not exist in the current context
                // Dummy(x7, 1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(14, 7),
                // (15,7): error CS0103: The name 'x7' does not exist in the current context
                // Dummy(x7, 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(15, 7),
                // (17,9): error CS0103: The name 'x7' does not exist in the current context
                //         x7);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(17, 9),
                // (18,7): error CS0103: The name 'x7' does not exist in the current context
                // Dummy(x7, 2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(18, 7)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").Single();
                VerifyModelForOutVar(model, x4Decl, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").Single();
                Assert.Equal(2, x5Decl.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Decl.Length);
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
                VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(5, x7Ref.Length);
                VerifyNotInScope(model, x7Ref[0]);
                VerifyNotInScope(model, x7Ref[1]);
                VerifyModelForOutVar(model, x7Decl, x7Ref[2]);
                VerifyNotInScope(model, x7Ref[3]);
                VerifyNotInScope(model, x7Ref[4]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(2, x8Ref.Length);
                VerifyModelForOutField(model, x8Decl, x8Ref);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(2, x9Ref.Length);
                VerifyModelForOutField(model, x9Decl[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[0]);

                var x10Decl = GetOutVarDeclarations(tree, "x10").ToArray();
                var x10Ref = GetReferences(tree, "x10").ToArray();
                Assert.Equal(2, x10Decl.Length);
                Assert.Equal(2, x10Ref.Length);
                VerifyModelForOutVar(model, x10Decl[0], x10Ref[0]);
                VerifyModelForOutField(model, x10Decl[1], x10Ref[1]);

                var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
                var x11Ref = GetReferences(tree, "x11").ToArray();
                Assert.Equal(3, x11Ref.Length);
                VerifyNotAnOutLocal(model, x11Ref[0]);
                VerifyModelForOutVar(model, x11Decl, x11Ref[1]);
                VerifyNotAnOutLocal(model, x11Ref[2]);

                var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
                var x12Ref = GetReferences(tree, "x12").ToArray();
                Assert.Equal(3, x12Ref.Length);
                VerifyModelForOutVar(model, x12Decl, x12Ref[0]);
                VerifyNotAnOutLocal(model, x12Ref[1]);
                VerifyNotAnOutLocal(model, x12Ref[2]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,41): error CS0841: Cannot use local variable 'x4' before it is declared
                    // Dummy((System.Func<object, bool>) (o => x4 && TakeOutParam(o, out var x4)));
                    Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(6, 41),
                    // (9,82): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    //                                                         TakeOutParam(o2, out var x5) && 
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(9, 82),
                    // (14,7): error CS0103: The name 'x7' does not exist in the current context
                    // Dummy(x7, 1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(14, 7),
                    // (15,7): error CS0103: The name 'x7' does not exist in the current context
                    // Dummy(x7, 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(15, 7),
                    // (17,9): error CS0103: The name 'x7' does not exist in the current context
                    //         x7);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(17, 9),
                    // (18,7): error CS0103: The name 'x7' does not exist in the current context
                    // Dummy(x7, 2); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(18, 7),
                    // (20,7): error CS0019: Operator '&&' cannot be applied to operands of type 'bool' and 'int'
                    // Dummy(TakeOutParam(true, out var x8) && x8, (System.Func<object, bool>) (o => TakeOutParam(o, out var y8) && x8));
                    Diagnostic(ErrorCode.ERR_BadBinaryOps, "TakeOutParam(true, out var x8) && x8").WithArguments("&&", "bool", "int").WithLocation(20, 7),
                    // (20,79): error CS0019: Operator '&&' cannot be applied to operands of type 'bool' and 'int'
                    // Dummy(TakeOutParam(true, out var x8) && x8, (System.Func<object, bool>) (o => TakeOutParam(o, out var y8) && x8));
                    Diagnostic(ErrorCode.ERR_BadBinaryOps, "TakeOutParam(o, out var y8) && x8").WithArguments("&&", "bool", "int").WithLocation(20, 79),
                    // (37,9): error CS0841: Cannot use local variable 'x12' before it is declared
                    //         x12);
                    Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x12").WithArguments("x12").WithLocation(37, 9),
                    // (47,13): error CS0128: A local variable or function named 'TakeOutParam' is already defined in this scope
                    // static bool TakeOutParam(bool y, out bool x) 
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "TakeOutParam").WithArguments("TakeOutParam").WithLocation(47, 13),
                    // (47,13): warning CS8321: The local function 'TakeOutParam' is declared but never used
                    // static bool TakeOutParam(bool y, out bool x) 
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "TakeOutParam").WithArguments("TakeOutParam").WithLocation(47, 13)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").Single();
                VerifyModelForOutVar(model, x4Decl, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").Single();
                Assert.Equal(2, x5Decl.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Decl.Length);
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl[0], x6Ref[0]);
                VerifyModelForOutVar(model, x6Decl[1], x6Ref[1]);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(5, x7Ref.Length);
                VerifyNotInScope(model, x7Ref[0]);
                VerifyNotInScope(model, x7Ref[1]);
                VerifyModelForOutVar(model, x7Decl, x7Ref[2]);
                VerifyNotInScope(model, x7Ref[3]);
                VerifyNotInScope(model, x7Ref[4]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(2, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(2, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[0]);

                var x10Decl = GetOutVarDeclarations(tree, "x10").ToArray();
                var x10Ref = GetReferences(tree, "x10").ToArray();
                Assert.Equal(2, x10Decl.Length);
                Assert.Equal(2, x10Ref.Length);
                VerifyModelForOutVar(model, x10Decl[0], x10Ref[0]);
                VerifyModelForOutVar(model, x10Decl[1], x10Ref[1]);

                var x11Decl = GetOutVarDeclarations(tree, "x11").Single();
                var x11Ref = GetReferences(tree, "x11").ToArray();
                Assert.Equal(3, x11Ref.Length);
                VerifyNotAnOutLocal(model, x11Ref[0]);
                VerifyModelForOutVar(model, x11Decl, x11Ref[1]);
                VerifyNotAnOutLocal(model, x11Ref[2]);

                var x12Decl = GetOutVarDeclarations(tree, "x12").Single();
                var x12Ref = GetReferences(tree, "x12").ToArray();
                Assert.Equal(3, x12Ref.Length);
                VerifyModelForOutVar(model, x12Decl, x12Ref[0]);
                VerifyNotAnOutLocal(model, x12Ref[1]);
                VerifyNotAnOutLocal(model, x12Ref[2]);
            }
        }

        [Fact]
        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
        public void GlobalCode_Lambda_02()
        {
            var source =
@"
System.Func<bool> l = () => TakeOutParam(1, out int x1) && Dummy(x1); 
System.Console.WriteLine(l());

static bool Dummy(int x) 
{
    System.Console.WriteLine(x);
    return true;
}

static bool TakeOutParam(int y, out int x) 
{
    x = y;
    return true;
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
            CompileAndVerify(compilation, expectedOutput: @"1
True");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_Lambda_03()
        {
            var source =
@"
System.Console.WriteLine(((System.Func<bool>)(() => TakeOutParam(1, out int x1) && Dummy(x1)))());

static bool Dummy(int x) 
{
    System.Console.WriteLine(x);
    return true;
}

static bool TakeOutParam(int y, out int x) 
{
    x = y;
    return true;
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
            CompileAndVerify(compilation, expectedOutput: @"1
True");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_Query_01()
        {
            var source =
@"
using System.Linq;

bool Dummy(params object[] x) {return true;}

var r01 = from x in new[] { TakeOutParam(1, out var y1) ? y1 : 0, y1}
            select x + y1;

Dummy(y1); 

var r02 = from x1 in new[] { TakeOutParam(1, out var y2) ? y2 : 0}
            from x2 in new[] { TakeOutParam(x1, out var z2) ? z2 : 0, z2, y2}
            select x1 + x2 + y2 + 
                    z2;

Dummy(z2); 

var r03 = from x1 in new[] { TakeOutParam(1, out var y3) ? y3 : 0}
            let x2 = TakeOutParam(x1, out var z3) && z3 > 0 && y3 < 0 
            select new { x1, x2, y3,
                        z3};

Dummy(z3); 

var r04 = from x1 in new[] { TakeOutParam(1, out var y4) ? y4 : 0}
            join x2 in new[] { TakeOutParam(2, out var z4) ? z4 : 0, z4, y4}
                    on x1 + y4 + z4 + (TakeOutParam(3, out var u4) ? u4 : 0) + 
                            v4 
                        equals x2 + y4 + z4 + (TakeOutParam(4, out var v4) ? v4 : 0) +
                            u4 
            select new { x1, x2, y4, z4, 
                        u4, v4 };

Dummy(z4); 
Dummy(u4); 
Dummy(v4); 

var r05 = from x1 in new[] { TakeOutParam(1, out var y5) ? y5 : 0}
            join x2 in new[] { TakeOutParam(2, out var z5) ? z5 : 0, z5, y5}
                    on x1 + y5 + z5 + (TakeOutParam(3, out var u5) ? u5 : 0) + 
                            v5 
                        equals x2 + y5 + z5 + (TakeOutParam(4, out var v5) ? v5 : 0) +
                            u5 
            into g
            select new { x1, y5, z5, g,
                        u5, v5 };

Dummy(z5); 
Dummy(u5); 
Dummy(v5); 

var r06 = from x in new[] { TakeOutParam(1, out var y6) ? y6 : 0}
            where x > y6 && TakeOutParam(1, out var z6) && z6 == 1
            select x + y6 +
                    z6;

Dummy(z6); 

var r07 = from x in new[] { TakeOutParam(1, out var y7) ? y7 : 0}
            orderby x > y7 && TakeOutParam(1, out var z7) && z7 == 
                    u7,
                    x > y7 && TakeOutParam(1, out var u7) && u7 == 
                    z7   
            select x + y7 +
                    z7 + u7;

Dummy(z7); 
Dummy(u7); 

var r08 = from x in new[] { TakeOutParam(1, out var y8) ? y8 : 0}
            select x > y8 && TakeOutParam(1, out var z8) && z8 == 1;

Dummy(z8); 

var r09 = from x in new[] { TakeOutParam(1, out var y9) ? y9 : 0}
            group x > y9 && TakeOutParam(1, out var z9) && z9 == 
                u9
            by
                x > y9 && TakeOutParam(1, out var u9) && u9 == 
                z9;   

Dummy(z9); 
Dummy(u9); 

var r10 = from x1 in new[] { TakeOutParam(1, out var y10) ? y10 : 0}
            from y10 in new[] { 1 }
            select x1 + y10;

var r11 = from x1 in new[] { TakeOutParam(1, out var y11) ? y11 : 0}
            let y11 = x1 + 1
            select x1 + y11;

static bool TakeOutParam<T>(T y, out T x) 
{
    x = y;
    return true;
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
                compilation.VerifyDiagnostics(
                // (14,21): error CS0103: The name 'z2' does not exist in the current context
                //                     z2;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(14, 21),
                // (21,25): error CS0103: The name 'z3' does not exist in the current context
                //                         z3};
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z3").WithArguments("z3").WithLocation(21, 25),
                // (28,29): error CS0103: The name 'v4' does not exist in the current context
                //                             v4 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(28, 29),
                // (30,29): error CS1938: The name 'u4' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                //                             u4 
                Diagnostic(ErrorCode.ERR_QueryInnerKey, "u4").WithArguments("u4").WithLocation(30, 29),
                // (32,25): error CS0103: The name 'u4' does not exist in the current context
                //                         u4, v4 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(32, 25),
                // (32,29): error CS0103: The name 'v4' does not exist in the current context
                //                         u4, v4 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(32, 29),
                // (41,29): error CS0103: The name 'v5' does not exist in the current context
                //                             v5 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(41, 29),
                // (43,29): error CS1938: The name 'u5' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                //                             u5 
                Diagnostic(ErrorCode.ERR_QueryInnerKey, "u5").WithArguments("u5").WithLocation(43, 29),
                // (46,25): error CS0103: The name 'u5' does not exist in the current context
                //                         u5, v5 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(46, 25),
                // (46,29): error CS0103: The name 'v5' does not exist in the current context
                //                         u5, v5 };
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(46, 29),
                // (55,21): error CS0103: The name 'z6' does not exist in the current context
                //                     z6;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z6").WithArguments("z6").WithLocation(55, 21),
                // (61,21): error CS0103: The name 'u7' does not exist in the current context
                //                     u7,
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(61, 21),
                // (63,21): error CS0103: The name 'z7' does not exist in the current context
                //                     z7   
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(63, 21),
                // (65,21): error CS0103: The name 'z7' does not exist in the current context
                //                     z7 + u7;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(65, 21),
                // (65,26): error CS0103: The name 'u7' does not exist in the current context
                //                     z7 + u7;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(65, 26),
                // (80,17): error CS0103: The name 'z9' does not exist in the current context
                //                 z9;   
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z9").WithArguments("z9").WithLocation(80, 17),
                // (77,17): error CS0103: The name 'u9' does not exist in the current context
                //                 u9
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u9").WithArguments("u9").WithLocation(77, 17),
                // (16,7): error CS0103: The name 'z2' does not exist in the current context
                // Dummy(z2); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(16, 7),
                // (23,7): error CS0103: The name 'z3' does not exist in the current context
                // Dummy(z3); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z3").WithArguments("z3").WithLocation(23, 7),
                // (35,7): error CS0103: The name 'u4' does not exist in the current context
                // Dummy(u4); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(35, 7),
                // (36,7): error CS0103: The name 'v4' does not exist in the current context
                // Dummy(v4); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(36, 7),
                // (49,7): error CS0103: The name 'u5' does not exist in the current context
                // Dummy(u5); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(49, 7),
                // (50,7): error CS0103: The name 'v5' does not exist in the current context
                // Dummy(v5); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(50, 7),
                // (57,7): error CS0103: The name 'z6' does not exist in the current context
                // Dummy(z6); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z6").WithArguments("z6").WithLocation(57, 7),
                // (67,7): error CS0103: The name 'z7' does not exist in the current context
                // Dummy(z7); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(67, 7),
                // (68,7): error CS0103: The name 'u7' does not exist in the current context
                // Dummy(u7); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(68, 7),
                // (73,7): error CS0103: The name 'z8' does not exist in the current context
                // Dummy(z8); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z8").WithArguments("z8").WithLocation(73, 7),
                // (82,7): error CS0103: The name 'z9' does not exist in the current context
                // Dummy(z9); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z9").WithArguments("z9").WithLocation(82, 7),
                // (83,7): error CS0103: The name 'u9' does not exist in the current context
                // Dummy(u9); 
                Diagnostic(ErrorCode.ERR_NameNotInContext, "u9").WithArguments("u9").WithLocation(83, 7)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var y1Decl = GetOutVarDeclarations(tree, "y1").Single();
                var y1Ref = GetReferences(tree, "y1").ToArray();
                Assert.Equal(4, y1Ref.Length);
                VerifyModelForOutField(model, y1Decl, y1Ref);

                var y2Decl = GetOutVarDeclarations(tree, "y2").Single();
                var y2Ref = GetReferences(tree, "y2").ToArray();
                Assert.Equal(3, y2Ref.Length);
                VerifyModelForOutField(model, y2Decl, y2Ref);

                var z2Decl = GetOutVarDeclarations(tree, "z2").Single();
                var z2Ref = GetReferences(tree, "z2").ToArray();
                Assert.Equal(4, z2Ref.Length);
                VerifyModelForOutVar(model, z2Decl, z2Ref[0], z2Ref[1]);
                VerifyNotInScope(model, z2Ref[2]);
                VerifyNotInScope(model, z2Ref[3]);

                var y3Decl = GetOutVarDeclarations(tree, "y3").Single();
                var y3Ref = GetReferences(tree, "y3").ToArray();
                Assert.Equal(3, y3Ref.Length);
                VerifyModelForOutField(model, y3Decl, y3Ref);

                var z3Decl = GetOutVarDeclarations(tree, "z3").Single();
                var z3Ref = GetReferences(tree, "z3").ToArray();
                Assert.Equal(3, z3Ref.Length);
                VerifyModelForOutVar(model, z3Decl, z3Ref[0]);
                VerifyNotInScope(model, z3Ref[1]);
                VerifyNotInScope(model, z3Ref[2]);

                var y4Decl = GetOutVarDeclarations(tree, "y4").Single();
                var y4Ref = GetReferences(tree, "y4").ToArray();
                Assert.Equal(5, y4Ref.Length);
                VerifyModelForOutField(model, y4Decl, y4Ref);

                var z4Decl = GetOutVarDeclarations(tree, "z4").Single();
                var z4Ref = GetReferences(tree, "z4").ToArray();
                Assert.Equal(6, z4Ref.Length);
                VerifyModelForOutField(model, z4Decl, z4Ref);

                var u4Decl = GetOutVarDeclarations(tree, "u4").Single();
                var u4Ref = GetReferences(tree, "u4").ToArray();
                Assert.Equal(4, u4Ref.Length);
                VerifyModelForOutVar(model, u4Decl, u4Ref[0]);
                VerifyNotInScope(model, u4Ref[1]);
                VerifyNotInScope(model, u4Ref[2]);
                VerifyNotInScope(model, u4Ref[3]);

                var v4Decl = GetOutVarDeclarations(tree, "v4").Single();
                var v4Ref = GetReferences(tree, "v4").ToArray();
                Assert.Equal(4, v4Ref.Length);
                VerifyNotInScope(model, v4Ref[0]);
                VerifyModelForOutVar(model, v4Decl, v4Ref[1]);
                VerifyNotInScope(model, v4Ref[2]);
                VerifyNotInScope(model, v4Ref[3]);

                var y5Decl = GetOutVarDeclarations(tree, "y5").Single();
                var y5Ref = GetReferences(tree, "y5").ToArray();
                Assert.Equal(5, y5Ref.Length);
                VerifyModelForOutField(model, y5Decl, y5Ref);

                var z5Decl = GetOutVarDeclarations(tree, "z5").Single();
                var z5Ref = GetReferences(tree, "z5").ToArray();
                Assert.Equal(6, z5Ref.Length);
                VerifyModelForOutField(model, z5Decl, z5Ref);

                var u5Decl = GetOutVarDeclarations(tree, "u5").Single();
                var u5Ref = GetReferences(tree, "u5").ToArray();
                Assert.Equal(4, u5Ref.Length);
                VerifyModelForOutVar(model, u5Decl, u5Ref[0]);
                VerifyNotInScope(model, u5Ref[1]);
                VerifyNotInScope(model, u5Ref[2]);
                VerifyNotInScope(model, u5Ref[3]);

                var v5Decl = GetOutVarDeclarations(tree, "v5").Single();
                var v5Ref = GetReferences(tree, "v5").ToArray();
                Assert.Equal(4, v5Ref.Length);
                VerifyNotInScope(model, v5Ref[0]);
                VerifyModelForOutVar(model, v5Decl, v5Ref[1]);
                VerifyNotInScope(model, v5Ref[2]);
                VerifyNotInScope(model, v5Ref[3]);

                var y6Decl = GetOutVarDeclarations(tree, "y6").Single();
                var y6Ref = GetReferences(tree, "y6").ToArray();
                Assert.Equal(3, y6Ref.Length);
                VerifyModelForOutField(model, y6Decl, y6Ref);

                var z6Decl = GetOutVarDeclarations(tree, "z6").Single();
                var z6Ref = GetReferences(tree, "z6").ToArray();
                Assert.Equal(3, z6Ref.Length);
                VerifyModelForOutVar(model, z6Decl, z6Ref[0]);
                VerifyNotInScope(model, z6Ref[1]);
                VerifyNotInScope(model, z6Ref[2]);

                var y7Decl = GetOutVarDeclarations(tree, "y7").Single();
                var y7Ref = GetReferences(tree, "y7").ToArray();
                Assert.Equal(4, y7Ref.Length);
                VerifyModelForOutField(model, y7Decl, y7Ref);

                var z7Decl = GetOutVarDeclarations(tree, "z7").Single();
                var z7Ref = GetReferences(tree, "z7").ToArray();
                Assert.Equal(4, z7Ref.Length);
                VerifyModelForOutVar(model, z7Decl, z7Ref[0]);
                VerifyNotInScope(model, z7Ref[1]);
                VerifyNotInScope(model, z7Ref[2]);
                VerifyNotInScope(model, z7Ref[3]);

                var u7Decl = GetOutVarDeclarations(tree, "u7").Single();
                var u7Ref = GetReferences(tree, "u7").ToArray();
                Assert.Equal(4, u7Ref.Length);
                VerifyNotInScope(model, u7Ref[0]);
                VerifyModelForOutVar(model, u7Decl, u7Ref[1]);
                VerifyNotInScope(model, u7Ref[2]);
                VerifyNotInScope(model, u7Ref[3]);

                var y8Decl = GetOutVarDeclarations(tree, "y8").Single();
                var y8Ref = GetReferences(tree, "y8").ToArray();
                Assert.Equal(2, y8Ref.Length);
                VerifyModelForOutField(model, y8Decl, y8Ref);

                var z8Decl = GetOutVarDeclarations(tree, "z8").Single();
                var z8Ref = GetReferences(tree, "z8").ToArray();
                Assert.Equal(2, z8Ref.Length);
                VerifyModelForOutVar(model, z8Decl, z8Ref[0]);
                VerifyNotInScope(model, z8Ref[1]);

                var y9Decl = GetOutVarDeclarations(tree, "y9").Single();
                var y9Ref = GetReferences(tree, "y9").ToArray();
                Assert.Equal(3, y9Ref.Length);
                VerifyModelForOutField(model, y9Decl, y9Ref);

                var z9Decl = GetOutVarDeclarations(tree, "z9").Single();
                var z9Ref = GetReferences(tree, "z9").ToArray();
                Assert.Equal(3, z9Ref.Length);
                VerifyModelForOutVar(model, z9Decl, z9Ref[0]);
                VerifyNotInScope(model, z9Ref[1]);
                VerifyNotInScope(model, z9Ref[2]);

                var u9Decl = GetOutVarDeclarations(tree, "u9").Single();
                var u9Ref = GetReferences(tree, "u9").ToArray();
                Assert.Equal(3, u9Ref.Length);
                VerifyNotInScope(model, u9Ref[0]);
                VerifyModelForOutVar(model, u9Decl, u9Ref[1]);
                VerifyNotInScope(model, u9Ref[2]);

                var y10Decl = GetOutVarDeclarations(tree, "y10").Single();
                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyModelForOutField(model, y10Decl, y10Ref[0]);
                VerifyNotAnOutField(model, y10Ref[1]);

                var y11Decl = GetOutVarDeclarations(tree, "y11").Single();
                var y11Ref = GetReferences(tree, "y11").ToArray();
                Assert.Equal(2, y11Ref.Length);
                VerifyModelForOutField(model, y11Decl, y11Ref[0]);
                VerifyNotAnOutField(model, y11Ref[1]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (14,21): error CS0103: The name 'z2' does not exist in the current context
                    //                     z2;
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(14, 21),
                    // (16,7): error CS0103: The name 'z2' does not exist in the current context
                    // Dummy(z2); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(16, 7),
                    // (21,25): error CS0103: The name 'z3' does not exist in the current context
                    //                         z3};
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z3").WithArguments("z3").WithLocation(21, 25),
                    // (23,7): error CS0103: The name 'z3' does not exist in the current context
                    // Dummy(z3); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z3").WithArguments("z3").WithLocation(23, 7),
                    // (28,29): error CS0103: The name 'v4' does not exist in the current context
                    //                             v4 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(28, 29),
                    // (30,29): error CS1938: The name 'u4' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                    //                             u4 
                    Diagnostic(ErrorCode.ERR_QueryInnerKey, "u4").WithArguments("u4").WithLocation(30, 29),
                    // (32,25): error CS0103: The name 'u4' does not exist in the current context
                    //                         u4, v4 };
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(32, 25),
                    // (32,29): error CS0103: The name 'v4' does not exist in the current context
                    //                         u4, v4 };
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(32, 29),
                    // (35,7): error CS0103: The name 'u4' does not exist in the current context
                    // Dummy(u4); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u4").WithArguments("u4").WithLocation(35, 7),
                    // (36,7): error CS0103: The name 'v4' does not exist in the current context
                    // Dummy(v4); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "v4").WithArguments("v4").WithLocation(36, 7),
                    // (41,29): error CS0103: The name 'v5' does not exist in the current context
                    //                             v5 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(41, 29),
                    // (43,29): error CS1938: The name 'u5' is not in scope on the right side of 'equals'.  Consider swapping the expressions on either side of 'equals'.
                    //                             u5 
                    Diagnostic(ErrorCode.ERR_QueryInnerKey, "u5").WithArguments("u5").WithLocation(43, 29),
                    // (46,25): error CS0103: The name 'u5' does not exist in the current context
                    //                         u5, v5 };
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(46, 25),
                    // (46,29): error CS0103: The name 'v5' does not exist in the current context
                    //                         u5, v5 };
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(46, 29),
                    // (49,7): error CS0103: The name 'u5' does not exist in the current context
                    // Dummy(u5); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u5").WithArguments("u5").WithLocation(49, 7),
                    // (50,7): error CS0103: The name 'v5' does not exist in the current context
                    // Dummy(v5); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "v5").WithArguments("v5").WithLocation(50, 7),
                    // (55,21): error CS0103: The name 'z6' does not exist in the current context
                    //                     z6;
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z6").WithArguments("z6").WithLocation(55, 21),
                    // (57,7): error CS0103: The name 'z6' does not exist in the current context
                    // Dummy(z6); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z6").WithArguments("z6").WithLocation(57, 7),
                    // (61,21): error CS0103: The name 'u7' does not exist in the current context
                    //                     u7,
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(61, 21),
                    // (63,21): error CS0103: The name 'z7' does not exist in the current context
                    //                     z7   
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(63, 21),
                    // (65,21): error CS0103: The name 'z7' does not exist in the current context
                    //                     z7 + u7;
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(65, 21),
                    // (65,26): error CS0103: The name 'u7' does not exist in the current context
                    //                     z7 + u7;
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(65, 26),
                    // (67,7): error CS0103: The name 'z7' does not exist in the current context
                    // Dummy(z7); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z7").WithArguments("z7").WithLocation(67, 7),
                    // (68,7): error CS0103: The name 'u7' does not exist in the current context
                    // Dummy(u7); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u7").WithArguments("u7").WithLocation(68, 7),
                    // (73,7): error CS0103: The name 'z8' does not exist in the current context
                    // Dummy(z8); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z8").WithArguments("z8").WithLocation(73, 7),
                    // (77,17): error CS0103: The name 'u9' does not exist in the current context
                    //                 u9
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u9").WithArguments("u9").WithLocation(77, 17),
                    // (80,17): error CS0103: The name 'z9' does not exist in the current context
                    //                 z9;   
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z9").WithArguments("z9").WithLocation(80, 17),
                    // (82,7): error CS0103: The name 'z9' does not exist in the current context
                    // Dummy(z9); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z9").WithArguments("z9").WithLocation(82, 7),
                    // (83,7): error CS0103: The name 'u9' does not exist in the current context
                    // Dummy(u9); 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "u9").WithArguments("u9").WithLocation(83, 7),
                    // (86,18): error CS1931: The range variable 'y10' conflicts with a previous declaration of 'y10'
                    //             from y10 in new[] { 1 }
                    Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y10").WithArguments("y10").WithLocation(86, 18),
                    // (90,17): error CS1931: The range variable 'y11' conflicts with a previous declaration of 'y11'
                    //             let y11 = x1 + 1
                    Diagnostic(ErrorCode.ERR_QueryRangeVariableOverrides, "y11").WithArguments("y11").WithLocation(90, 17)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var y1Decl = GetOutVarDeclarations(tree, "y1").Single();
                var y1Ref = GetReferences(tree, "y1").ToArray();
                Assert.Equal(4, y1Ref.Length);
                VerifyModelForOutVar(model, y1Decl, y1Ref);

                var y2Decl = GetOutVarDeclarations(tree, "y2").Single();
                var y2Ref = GetReferences(tree, "y2").ToArray();
                Assert.Equal(3, y2Ref.Length);
                VerifyModelForOutVar(model, y2Decl, y2Ref);

                var z2Decl = GetOutVarDeclarations(tree, "z2").Single();
                var z2Ref = GetReferences(tree, "z2").ToArray();
                Assert.Equal(4, z2Ref.Length);
                VerifyModelForOutVar(model, z2Decl, z2Ref[0], z2Ref[1]);
                VerifyNotInScope(model, z2Ref[2]);
                VerifyNotInScope(model, z2Ref[3]);

                var y3Decl = GetOutVarDeclarations(tree, "y3").Single();
                var y3Ref = GetReferences(tree, "y3").ToArray();
                Assert.Equal(3, y3Ref.Length);
                VerifyModelForOutVar(model, y3Decl, y3Ref);

                var z3Decl = GetOutVarDeclarations(tree, "z3").Single();
                var z3Ref = GetReferences(tree, "z3").ToArray();
                Assert.Equal(3, z3Ref.Length);
                VerifyModelForOutVar(model, z3Decl, z3Ref[0]);
                VerifyNotInScope(model, z3Ref[1]);
                VerifyNotInScope(model, z3Ref[2]);

                var y4Decl = GetOutVarDeclarations(tree, "y4").Single();
                var y4Ref = GetReferences(tree, "y4").ToArray();
                Assert.Equal(5, y4Ref.Length);
                VerifyModelForOutVar(model, y4Decl, y4Ref);

                var z4Decl = GetOutVarDeclarations(tree, "z4").Single();
                var z4Ref = GetReferences(tree, "z4").ToArray();
                Assert.Equal(6, z4Ref.Length);
                VerifyModelForOutVar(model, z4Decl, z4Ref);

                var u4Decl = GetOutVarDeclarations(tree, "u4").Single();
                var u4Ref = GetReferences(tree, "u4").ToArray();
                Assert.Equal(4, u4Ref.Length);
                VerifyModelForOutVar(model, u4Decl, u4Ref[0]);
                VerifyNotInScope(model, u4Ref[1]);
                VerifyNotInScope(model, u4Ref[2]);
                VerifyNotInScope(model, u4Ref[3]);

                var v4Decl = GetOutVarDeclarations(tree, "v4").Single();
                var v4Ref = GetReferences(tree, "v4").ToArray();
                Assert.Equal(4, v4Ref.Length);
                VerifyNotInScope(model, v4Ref[0]);
                VerifyModelForOutVar(model, v4Decl, v4Ref[1]);
                VerifyNotInScope(model, v4Ref[2]);
                VerifyNotInScope(model, v4Ref[3]);

                var y5Decl = GetOutVarDeclarations(tree, "y5").Single();
                var y5Ref = GetReferences(tree, "y5").ToArray();
                Assert.Equal(5, y5Ref.Length);
                VerifyModelForOutVar(model, y5Decl, y5Ref);

                var z5Decl = GetOutVarDeclarations(tree, "z5").Single();
                var z5Ref = GetReferences(tree, "z5").ToArray();
                Assert.Equal(6, z5Ref.Length);
                VerifyModelForOutVar(model, z5Decl, z5Ref);

                var u5Decl = GetOutVarDeclarations(tree, "u5").Single();
                var u5Ref = GetReferences(tree, "u5").ToArray();
                Assert.Equal(4, u5Ref.Length);
                VerifyModelForOutVar(model, u5Decl, u5Ref[0]);
                VerifyNotInScope(model, u5Ref[1]);
                VerifyNotInScope(model, u5Ref[2]);
                VerifyNotInScope(model, u5Ref[3]);

                var v5Decl = GetOutVarDeclarations(tree, "v5").Single();
                var v5Ref = GetReferences(tree, "v5").ToArray();
                Assert.Equal(4, v5Ref.Length);
                VerifyNotInScope(model, v5Ref[0]);
                VerifyModelForOutVar(model, v5Decl, v5Ref[1]);
                VerifyNotInScope(model, v5Ref[2]);
                VerifyNotInScope(model, v5Ref[3]);

                var y6Decl = GetOutVarDeclarations(tree, "y6").Single();
                var y6Ref = GetReferences(tree, "y6").ToArray();
                Assert.Equal(3, y6Ref.Length);
                VerifyModelForOutVar(model, y6Decl, y6Ref);

                var z6Decl = GetOutVarDeclarations(tree, "z6").Single();
                var z6Ref = GetReferences(tree, "z6").ToArray();
                Assert.Equal(3, z6Ref.Length);
                VerifyModelForOutVar(model, z6Decl, z6Ref[0]);
                VerifyNotInScope(model, z6Ref[1]);
                VerifyNotInScope(model, z6Ref[2]);

                var y7Decl = GetOutVarDeclarations(tree, "y7").Single();
                var y7Ref = GetReferences(tree, "y7").ToArray();
                Assert.Equal(4, y7Ref.Length);
                VerifyModelForOutVar(model, y7Decl, y7Ref);

                var z7Decl = GetOutVarDeclarations(tree, "z7").Single();
                var z7Ref = GetReferences(tree, "z7").ToArray();
                Assert.Equal(4, z7Ref.Length);
                VerifyModelForOutVar(model, z7Decl, z7Ref[0]);
                VerifyNotInScope(model, z7Ref[1]);
                VerifyNotInScope(model, z7Ref[2]);
                VerifyNotInScope(model, z7Ref[3]);

                var u7Decl = GetOutVarDeclarations(tree, "u7").Single();
                var u7Ref = GetReferences(tree, "u7").ToArray();
                Assert.Equal(4, u7Ref.Length);
                VerifyNotInScope(model, u7Ref[0]);
                VerifyModelForOutVar(model, u7Decl, u7Ref[1]);
                VerifyNotInScope(model, u7Ref[2]);
                VerifyNotInScope(model, u7Ref[3]);

                var y8Decl = GetOutVarDeclarations(tree, "y8").Single();
                var y8Ref = GetReferences(tree, "y8").ToArray();
                Assert.Equal(2, y8Ref.Length);
                VerifyModelForOutVar(model, y8Decl, y8Ref);

                var z8Decl = GetOutVarDeclarations(tree, "z8").Single();
                var z8Ref = GetReferences(tree, "z8").ToArray();
                Assert.Equal(2, z8Ref.Length);
                VerifyModelForOutVar(model, z8Decl, z8Ref[0]);
                VerifyNotInScope(model, z8Ref[1]);

                var y9Decl = GetOutVarDeclarations(tree, "y9").Single();
                var y9Ref = GetReferences(tree, "y9").ToArray();
                Assert.Equal(3, y9Ref.Length);
                VerifyModelForOutVar(model, y9Decl, y9Ref);

                var z9Decl = GetOutVarDeclarations(tree, "z9").Single();
                var z9Ref = GetReferences(tree, "z9").ToArray();
                Assert.Equal(3, z9Ref.Length);
                VerifyModelForOutVar(model, z9Decl, z9Ref[0]);
                VerifyNotInScope(model, z9Ref[1]);
                VerifyNotInScope(model, z9Ref[2]);

                var u9Decl = GetOutVarDeclarations(tree, "u9").Single();
                var u9Ref = GetReferences(tree, "u9").ToArray();
                Assert.Equal(3, u9Ref.Length);
                VerifyNotInScope(model, u9Ref[0]);
                VerifyModelForOutVar(model, u9Decl, u9Ref[1]);
                VerifyNotInScope(model, u9Ref[2]);

                var y10Decl = GetOutVarDeclarations(tree, "y10").Single();
                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyModelForOutVar(model, y10Decl, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var y11Decl = GetOutVarDeclarations(tree, "y11").Single();
                var y11Ref = GetReferences(tree, "y11").ToArray();
                Assert.Equal(2, y11Ref.Length);
                VerifyModelForOutVar(model, y11Decl, y11Ref[0]);
                VerifyNotAnOutLocal(model, y11Ref[1]);
            }
        }

        [Fact]
        public void GlobalCode_Query_02()
        {
            var source =
@"
using System.Linq;

var res = from x1 in new[] { TakeOutParam(1, out var y1) && Print(y1) ? 2 : 0}
            select Print(x1);

res.ToArray(); 

static bool TakeOutParam<T>(T y, out T x) 
{
    x = y;
    return true;
}

static bool Print(object x) 
{
    System.Console.WriteLine(x);
    return true;
}
";
            var compilation = CreateCompilationWithMscorlib461(source, new[] { SystemCoreRef }, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"1
2");

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var yDecl = GetOutVarDeclarations(tree, "y1").Single();
            var yRef = GetReferences(tree, "y1").Single();
            VerifyModelForOutField(model, yDecl, yRef);
        }

        [Fact]
        public void GlobalCode_Using_01()
        {
            var source =
@"
System.IDisposable Dummy(params object[] x) {return null;}

using (Dummy(TakeOutParam(true, out var x1), x1))
{
    Dummy(x1);
}
 
using (Dummy(TakeOutParam(true, out var x2), x2))
    Dummy(x2);
 
var x4 = 11;
Dummy(x4);

using (Dummy(TakeOutParam(true, out var x4), x4))
    Dummy(x4);
 
using (Dummy(x6 && TakeOutParam(true, out var x6)))
    Dummy(x6);
 
using (Dummy(TakeOutParam(true, out var x7) && x7))
{
    var x7 = 12;
    Dummy(x7);
}
 
using (Dummy(TakeOutParam(true, out var x8), x8))
    Dummy(x8);

System.Console.WriteLine(x8);
 
using (Dummy(TakeOutParam(true, out var x9), x9))
{   
    Dummy(x9);
    using (Dummy(TakeOutParam(true, out var x9), x9)) // 2
        Dummy(x9);
}

using (Dummy(TakeOutParam(y10, out var x10), x10))
{   
    var y10 = 12;
    Dummy(y10);
}

//    using (Dummy(TakeOutParam(y11, out var x11), x11))
//    {   
//        let y11 = 12;
//        Dummy(y11);
//    }

using (Dummy(TakeOutParam(y12, out var x12), x12))
    var y12 = 12;

//    using (Dummy(TakeOutParam(y13, out var x13), x13))
//        let y13 = 12;
 
using (Dummy(TakeOutParam(1, out var x14), 
                TakeOutParam(2, out var x14), 
                x14))
{
    Dummy(x14);
}

static bool TakeOutParam<T>(T y, out T x) 
{
    x = y;
    return true;
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
                compilation.VerifyDiagnostics(
                // (52,5): error CS1023: Embedded statement cannot be a declaration or labeled statement
                //     var y12 = 12;
                Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(52, 5),
                // (18,14): error CS0841: Cannot use local variable 'x6' before it is declared
                // using (Dummy(x6 && TakeOutParam(true, out var x6)))
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(18, 14),
                // (23,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     var x7 = 12;
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(23, 9),
                // (30,26): error CS0103: The name 'x8' does not exist in the current context
                // System.Console.WriteLine(x8);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(30, 26),
                // (35,45): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     using (Dummy(TakeOutParam(true, out var x9), x9)) // 2
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(35, 45),
                // (39,27): error CS0103: The name 'y10' does not exist in the current context
                // using (Dummy(TakeOutParam(y10, out var x10), x10))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(39, 27),
                // (51,27): error CS0103: The name 'y12' does not exist in the current context
                // using (Dummy(TakeOutParam(y12, out var x12), x12))
                Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(51, 27),
                // (58,41): error CS0128: A local variable or function named 'x14' is already defined in this scope
                //                 TakeOutParam(2, out var x14), 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(58, 41),
                // (52,9): warning CS0219: The variable 'y12' is assigned but its value is never used
                //     var y12 = 12;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(52, 9)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").ToArray();
                Assert.Equal(2, x2Ref.Length);
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
                var x10Ref = GetReferences(tree, "x10").Single();
                VerifyModelForOutVar(model, x10Decl, x10Ref);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var y12Ref = GetReferences(tree, "y12").Single();
                VerifyNotInScope(model, y12Ref);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (15,41): error CS0136: A local or parameter named 'x4' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // using (Dummy(TakeOutParam(true, out var x4), x4))
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x4").WithArguments("x4").WithLocation(15, 41),
                    // (18,14): error CS0841: Cannot use local variable 'x6' before it is declared
                    // using (Dummy(x6 && TakeOutParam(true, out var x6)))
                    Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x6").WithArguments("x6").WithLocation(18, 14),
                    // (23,9): error CS0136: A local or parameter named 'x7' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     var x7 = 12;
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x7").WithArguments("x7").WithLocation(23, 9),
                    // (30,26): error CS0103: The name 'x8' does not exist in the current context
                    // System.Console.WriteLine(x8);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x8").WithArguments("x8").WithLocation(30, 26),
                    // (35,45): error CS0136: A local or parameter named 'x9' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     using (Dummy(TakeOutParam(true, out var x9), x9)) // 2
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x9").WithArguments("x9").WithLocation(35, 45),
                    // (39,27): error CS0103: The name 'y10' does not exist in the current context
                    // using (Dummy(TakeOutParam(y10, out var x10), x10))
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "y10").WithArguments("y10").WithLocation(39, 27),
                    // (51,27): error CS0103: The name 'y12' does not exist in the current context
                    // using (Dummy(TakeOutParam(y12, out var x12), x12))
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "y12").WithArguments("y12").WithLocation(51, 27),
                    // (52,5): error CS1023: Embedded statement cannot be a declaration or labeled statement
                    //     var y12 = 12;
                    Diagnostic(ErrorCode.ERR_BadEmbeddedStmt, "var y12 = 12;").WithLocation(52, 5),
                    // (52,9): warning CS0219: The variable 'y12' is assigned but its value is never used
                    //     var y12 = 12;
                    Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "y12").WithArguments("y12").WithLocation(52, 9),
                    // (58,41): error CS0128: A local variable or function named 'x14' is already defined in this scope
                    //                 TakeOutParam(2, out var x14), 
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x14").WithArguments("x14").WithLocation(58, 41)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").ToArray();
                Assert.Equal(2, x2Ref.Length);
                VerifyModelForOutVar(model, x2Decl, x2Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").Single();
                var x4Ref = GetReferences(tree, "x4").ToArray();
                Assert.Equal(3, x4Ref.Length);
                VerifyNotAnOutLocal(model, x4Ref[0]);
                VerifyModelForOutVar(model, x4Decl, x4Ref[1], x4Ref[2]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(2, x6Ref.Length);
                VerifyModelForOutVar(model, x6Decl, x6Ref);

                var x7Decl = GetOutVarDeclarations(tree, "x7").Single();
                var x7Ref = GetReferences(tree, "x7").ToArray();
                Assert.Equal(2, x7Ref.Length);
                VerifyModelForOutVar(model, x7Decl, x7Ref[0]);
                VerifyNotAnOutLocal(model, x7Ref[1]);

                var x8Decl = GetOutVarDeclarations(tree, "x8").Single();
                var x8Ref = GetReferences(tree, "x8").ToArray();
                Assert.Equal(3, x8Ref.Length);
                VerifyModelForOutVar(model, x8Decl, x8Ref[0], x8Ref[1]);
                VerifyNotInScope(model, x8Ref[2]);

                var x9Decl = GetOutVarDeclarations(tree, "x9").ToArray();
                var x9Ref = GetReferences(tree, "x9").ToArray();
                Assert.Equal(2, x9Decl.Length);
                Assert.Equal(4, x9Ref.Length);
                VerifyModelForOutVar(model, x9Decl[0], x9Ref[0], x9Ref[1]);
                VerifyModelForOutVar(model, x9Decl[1], x9Ref[2], x9Ref[3]);

                var x10Decl = GetOutVarDeclarations(tree, "x10").Single();
                var x10Ref = GetReferences(tree, "x10").Single();
                VerifyModelForOutVar(model, x10Decl, x10Ref);

                var y10Ref = GetReferences(tree, "y10").ToArray();
                Assert.Equal(2, y10Ref.Length);
                VerifyNotInScope(model, y10Ref[0]);
                VerifyNotAnOutLocal(model, y10Ref[1]);

                var y12Ref = GetReferences(tree, "y12").Single();
                VerifyNotInScope(model, y12Ref);

                var x14Decl = GetOutVarDeclarations(tree, "x14").ToArray();
                var x14Ref = GetReferences(tree, "x14").ToArray();
                Assert.Equal(2, x14Decl.Length);
                Assert.Equal(2, x14Ref.Length);
                VerifyModelForOutVar(model, x14Decl[0], x14Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x14Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_Using_02()
        {
            var source =
@"
using (System.IDisposable d1 = Dummy(new C(""a""), TakeOutParam(new C(""b""), out var x1)),
                            d2 = Dummy(new C(""c""), TakeOutParam(new C(""d""), out var x2)))
{
    System.Console.WriteLine(d1);
    System.Console.WriteLine(x1);
    System.Console.WriteLine(d2);
    System.Console.WriteLine(x2);
}

using (Dummy(new C(""e""), TakeOutParam(new C(""f""), out var x1)))
{
    System.Console.WriteLine(x1);
}

static System.IDisposable Dummy(System.IDisposable x, params object[] y) {return x;}

static bool TakeOutParam<T>(T y, out T x) 
{
    x = y;
    return true;
}

class C : System.IDisposable
{
    private readonly string _val;

    public C(string val)
    {
        _val = val;
    }

    public void Dispose()
    {
        System.Console.WriteLine(""Disposing {0}"", _val);
    }

    public override string ToString()
    {
        return _val;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
            CompileAndVerify(compilation, expectedOutput:
@"a
b
c
d
Disposing c
Disposing a
f
Disposing e");
        }

        [Fact]
        public void GlobalCode_ExpressionStatement_01()
        {
            string source =
@"
H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
H.TakeOutParam(2, out int x2);

H.TakeOutParam(3, out int x3);
object x3;

H.Dummy(H.TakeOutParam(41, out int x4),
        H.TakeOutParam(42, out int x4));
Test();
void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,27): error CS0102: The type 'Script' already contains a definition for 'x2'
                // H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 27),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,36): error CS0102: The type 'Script' already contains a definition for 'x4'
                //         H.TakeOutParam(42, out int x4))
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 36),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,27): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 27),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,36): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //         H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 36),
                    // (13,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(13, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_ExpressionStatement_02()
        {
            string source =
@"
H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
H.TakeOutParam(2, out var x2);

H.TakeOutParam(3, out var x3);
object x3;

H.Dummy(H.TakeOutParam(41, out var x4),
        H.TakeOutParam(42, out var x4));
Test();
void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,27): error CS0102: The type 'Script' already contains a definition for 'x2'
                // H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 27),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,36): error CS0102: The type 'Script' already contains a definition for 'x4'
                //         H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 36),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,27): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 27),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,36): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //         H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 36),
                    // (13,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(13, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_ExpressionStatement_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
H.TakeOutParam(1, out var x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_IfStatement_01()
        {
            string source =
@"
if (H.TakeOutParam(1, out int x1)) {}
H.Dummy(x1);

object x2;
if (H.TakeOutParam(2, out int x2)) {}

if (H.TakeOutParam(3, out int x3)) {}
object x3;

if (H.Dummy(H.TakeOutParam(41, out int x4),
            H.TakeOutParam(42, out int x4))) {}

if (H.TakeOutParam(51, out int x5)) 
{
    H.TakeOutParam(""52"", out string x5);
    H.Dummy(x5);
}
H.Dummy(x5);

int x6 = 6;
if (H.Dummy()) 
{
    string x6 = ""6"";
    H.Dummy(x6);
}

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,31): error CS0102: The type 'Script' already contains a definition for 'x2'
                // if (H.TakeOutParam(2, out int x2)) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 31),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,40): error CS0102: The type 'Script' already contains a definition for 'x4'
                //             H.TakeOutParam(42, out int x4))) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 40),
                // (30,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(30, 17),
                // (30,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(30, 21),
                // (30,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(30, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,31): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // if (H.TakeOutParam(2, out int x2)) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 31),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,40): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //             H.TakeOutParam(42, out int x4))) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 40),
                    // (16,37): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out string x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 37),
                    // (21,5): warning CS0219: The variable 'x6' is assigned but its value is never used
                    // int x6 = 6;
                    Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x6").WithArguments("x6").WithLocation(21, 5),
                    // (24,12): error CS0136: A local or parameter named 'x6' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     string x6 = "6";
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x6").WithArguments("x6").WithLocation(24, 12),
                    // (33,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(33, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }
        }

        [Fact]
        public void GlobalCode_IfStatement_02()
        {
            string source =
@"
if (H.TakeOutParam(1, out var x1)) {}
H.Dummy(x1);

object x2;
if (H.TakeOutParam(2, out var x2)) {}

if (H.TakeOutParam(3, out var x3)) {}
object x3;

if (H.Dummy(H.TakeOutParam(41, out var x4),
            H.TakeOutParam(42, out var x4))) {}

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

if (H.TakeOutParam(51, out var x5)) 
{
    H.TakeOutParam(""52"", out var x5);
    H.Dummy(x5);
}
H.Dummy(x5);

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,31): error CS0102: The type 'Script' already contains a definition for 'x2'
                // if (H.TakeOutParam(2, out var x2)) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 31),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,40): error CS0102: The type 'Script' already contains a definition for 'x4'
                //             H.TakeOutParam(42, out var x4))) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 40),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl[0], x5Ref[0], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[1]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,31): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // if (H.TakeOutParam(2, out var x2)) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 31),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,40): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //             H.TakeOutParam(42, out var x4))) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 40),
                    // (16,29): error CS0841: Cannot use local variable 'x5' before it is declared
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x5").WithArguments("x5").WithLocation(16, 29),
                    // (21,34): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out var x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(21, 34),
                    // (26,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(26, 1),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[0], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[1]);
            }
        }

        [Fact]
        public void GlobalCode_IfStatement_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
if (H.TakeOutParam(1, out var x1)) 
{
    H.TakeOutParam(""11"", out var x1);
    System.Console.WriteLine(x1);
}
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
11
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void GlobalCode_IfStatement_04()
        {
            string source =
@"
System.Console.WriteLine(x1);
if (H.TakeOutParam(1, out var x1)) 
    H.Dummy(H.TakeOutParam(""11"", out var x1), x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static void Dummy(object x, object y)
    {
        System.Console.WriteLine(y);
    }

    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
11
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void GlobalCode_YieldReturnStatement_01()
        {
            string source =
@"
yield return H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
yield return H.TakeOutParam(2, out int x2);

yield return H.TakeOutParam(3, out int x3);
object x3;

yield return H.Dummy(H.TakeOutParam(41, out int x4),
                     H.TakeOutParam(42, out int x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,40): error CS0102: The type 'Script' already contains a definition for 'x2'
                // yield return H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 40),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,49): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                      H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 49),
                // (2,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.TakeOutParam(1, out int x1);
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(2, 1),
                // (6,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(6, 1),
                // (8,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.TakeOutParam(3, out int x3);
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(8, 1),
                // (11,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.Dummy(H.TakeOutParam(41, out int x4),
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(11, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,1): error CS1624: The body of '<top-level-statements-entry-point>' cannot be an iterator block because 'void' is not an iterator interface type
                    // yield return H.TakeOutParam(1, out int x1);
                    Diagnostic(ErrorCode.ERR_BadIteratorReturn, "yield return H.TakeOutParam(1, out int x1);").WithArguments("<top-level-statements-entry-point>", "void").WithLocation(2, 1),
                    // (6,40): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // yield return H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 40),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,49): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                      H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 49),
                    // (19,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(19, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_YieldReturnStatement_02()
        {
            string source =
@"
yield return H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
yield return H.TakeOutParam(2, out var x2);

yield return H.TakeOutParam(3, out var x3);
object x3;

yield return H.Dummy(H.TakeOutParam(41, out var x4),
                     H.TakeOutParam(42, out var x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,40): error CS0102: The type 'Script' already contains a definition for 'x2'
                // yield return H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 40),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,49): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                      H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 49),
                // (2,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.TakeOutParam(1, out var x1);
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(2, 1),
                // (6,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(6, 1),
                // (8,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.TakeOutParam(3, out var x3);
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(8, 1),
                // (11,1): error CS7020: Cannot use 'yield' in top-level script code
                // yield return H.Dummy(H.TakeOutParam(41, out var x4),
                Diagnostic(ErrorCode.ERR_YieldNotAllowedInScript, "yield").WithLocation(11, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);
                Assert.Equal("System.Int32", ((IFieldSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(x1Decl.VariableDesignation())).Type.ToTestDisplayString());

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,1): error CS1624: The body of '<top-level-statements-entry-point>' cannot be an iterator block because 'void' is not an iterator interface type
                    // yield return H.TakeOutParam(1, out var x1);
                    Diagnostic(ErrorCode.ERR_BadIteratorReturn, "yield return H.TakeOutParam(1, out var x1);").WithArguments("<top-level-statements-entry-point>", "void").WithLocation(2, 1),
                    // (6,40): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // yield return H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 40),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,49): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                      H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 49),
                    // (19,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(19, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_ReturnStatement_01()
        {
            string source =
@"
return H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
return H.TakeOutParam(2, out int x2);

return H.TakeOutParam(3, out int x3);
object x3;

return H.Dummy(H.TakeOutParam(41, out int x4),
               H.TakeOutParam(42, out int x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,34): error CS0102: The type 'Script' already contains a definition for 'x2'
                // return H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 34),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,43): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 43),
                // (3,1): warning CS0162: Unreachable code detected
                // H.Dummy(x1);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.TakeOutParam(1, out int x1);
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, "H.TakeOutParam(1, out int x1)").WithArguments("bool", "int").WithLocation(2, 8),
                    // (3,1): warning CS0162: Unreachable code detected
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                    // (6,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, "H.TakeOutParam(2, out int x2)").WithArguments("bool", "int").WithLocation(6, 8),
                    // (6,34): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // return H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 34),
                    // (8,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.TakeOutParam(3, out int x3);
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, "H.TakeOutParam(3, out int x3)").WithArguments("bool", "int").WithLocation(8, 8),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (11,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.Dummy(H.TakeOutParam(41, out int x4),
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, @"H.Dummy(H.TakeOutParam(41, out int x4),
               H.TakeOutParam(42, out int x4))").WithArguments("bool", "int").WithLocation(11, 8),
                    // (12,43): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 43),
                    // (14,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(14, 6)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_ReturnStatement_02()
        {
            string source =
@"
return H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
return H.TakeOutParam(2, out var x2);

return H.TakeOutParam(3, out var x3);
object x3;

return H.Dummy(H.TakeOutParam(41, out var x4),
               H.TakeOutParam(42, out var x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,34): error CS0102: The type 'Script' already contains a definition for 'x2'
                // return H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 34),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,43): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 43),
                // (3,1): warning CS0162: Unreachable code detected
                // H.Dummy(x1);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.TakeOutParam(1, out var x1);
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, "H.TakeOutParam(1, out var x1)").WithArguments("bool", "int").WithLocation(2, 8),
                    // (3,1): warning CS0162: Unreachable code detected
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                    // (6,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, "H.TakeOutParam(2, out var x2)").WithArguments("bool", "int").WithLocation(6, 8),
                    // (6,34): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // return H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 34),
                    // (8,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.TakeOutParam(3, out var x3);
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, "H.TakeOutParam(3, out var x3)").WithArguments("bool", "int").WithLocation(8, 8),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (11,8): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                    // return H.Dummy(H.TakeOutParam(41, out var x4),
                    Diagnostic(ErrorCode.ERR_NoImplicitConv, @"H.Dummy(H.TakeOutParam(41, out var x4),
               H.TakeOutParam(42, out var x4))").WithArguments("bool", "int").WithLocation(11, 8),
                    // (12,43): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 43),
                    // (14,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(14, 6)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_ReturnStatement_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
Test();
return H.Dummy(H.TakeOutParam(1, out var x1), x1);

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool Dummy(object x, object y) 
    {
        System.Console.WriteLine(y);
        return true;
    }
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
0
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_ThrowStatement_01()
        {
            string source =
@"
throw H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
throw H.TakeOutParam(2, out int x2);

throw H.TakeOutParam(3, out int x3);
object x3;

throw H.Dummy(H.TakeOutParam(41, out int x4),
              H.TakeOutParam(42, out int x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

Test();

class H
{
    public static System.Exception Dummy(params object[] x) {return null;}
    public static System.Exception TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,33): error CS0102: The type 'Script' already contains a definition for 'x2'
                // throw H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 33),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,42): error CS0102: The type 'Script' already contains a definition for 'x4'
                //               H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 42),
                // (3,1): warning CS0162: Unreachable code detected
                // H.Dummy(x1);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,1): warning CS0162: Unreachable code detected
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                    // (6,33): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // throw H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 33),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,42): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //               H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 42)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_ThrowStatement_02()
        {
            string source =
@"
throw H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
throw H.TakeOutParam(2, out var x2);

throw H.TakeOutParam(3, out var x3);
object x3;

throw H.Dummy(H.TakeOutParam(41, out var x4),
              H.TakeOutParam(42, out var x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

Test();

class H
{
    public static System.Exception Dummy(params object[] x) {return null;}
    public static System.Exception TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,33): error CS0102: The type 'Script' already contains a definition for 'x2'
                // throw H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 33),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,42): error CS0102: The type 'Script' already contains a definition for 'x4'
                //               H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 42),
                // (3,1): warning CS0162: Unreachable code detected
                // H.Dummy(x1);
                Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);
                Assert.Equal("System.Int32", ((IFieldSymbol)compilation.GetSemanticModel(tree).GetDeclaredSymbol(x1Decl.VariableDesignation())).Type.ToTestDisplayString());

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,1): warning CS0162: Unreachable code detected
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.WRN_UnreachableCode, "H").WithLocation(3, 1),
                    // (6,33): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // throw H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 33),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,42): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //               H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 42)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_SwitchStatement_01()
        {
            string source =
@"
switch (H.TakeOutParam(1, out int x1)) {default: break;}
H.Dummy(x1);

object x2;
switch (H.TakeOutParam(2, out int x2)) {default: break;}

switch (H.TakeOutParam(3, out int x3)) {default: break;}
object x3;

switch (H.Dummy(H.TakeOutParam(41, out int x4),
                H.TakeOutParam(42, out int x4))) {default: break;}

switch (H.TakeOutParam(51, out int x5)) 
{
default:
    H.TakeOutParam(""52"", out string x5);
    H.Dummy(x5);
    break;
}
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,35): error CS0102: The type 'Script' already contains a definition for 'x2'
                // switch (H.TakeOutParam(2, out int x2)) {default: break;}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 35),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,44): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                 H.TakeOutParam(42, out int x4))) {default: break;}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 44),
                // (25,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(25, 17),
                // (25,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(25, 21),
                // (25,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(25, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,35): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // switch (H.TakeOutParam(2, out int x2)) {default: break;}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 35),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,44): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                 H.TakeOutParam(42, out int x4))) {default: break;}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 44),
                    // (17,37): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out string x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(17, 37),
                    // (28,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(28, 1),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }
        }

        [Fact]
        public void GlobalCode_SwitchStatement_02()
        {
            string source =
@"
switch (H.TakeOutParam(1, out var x1)) {default: break;}
H.Dummy(x1);

object x2;
switch (H.TakeOutParam(2, out var x2)) {default: break;}

switch (H.TakeOutParam(3, out var x3)) {default: break;}
object x3;

switch (H.Dummy(H.TakeOutParam(41, out var x4),
                H.TakeOutParam(42, out var x4))) {default: break;}

switch (H.TakeOutParam(51, out var x5)) 
{
default:
    H.TakeOutParam(""52"", out var x5);
    H.Dummy(x5);
    break;
}
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,35): error CS0102: The type 'Script' already contains a definition for 'x2'
                // switch (H.TakeOutParam(2, out var x2)) {default: break;}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 35),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,44): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                 H.TakeOutParam(42, out var x4))) {default: break;}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 44),
                // (25,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(25, 17),
                // (25,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(25, 21),
                // (25,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(25, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,35): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // switch (H.TakeOutParam(2, out var x2)) {default: break;}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 35),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,44): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                 H.TakeOutParam(42, out var x4))) {default: break;}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 44),
                    // (17,34): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out var x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(17, 34),
                    // (28,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(28, 1),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }
        }

        [Fact]
        public void GlobalCode_SwitchStatement_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
switch (H.TakeOutParam(1, out var x1)) 
{
default:
    H.TakeOutParam(""11"", out var x1);
    System.Console.WriteLine(x1);
    break;
}
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
11
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void GlobalCode_WhileStatement_01()
        {
            string source =
@"
while (H.TakeOutParam(1, out int x1)) {}
H.Dummy(x1);

object x2;
while (H.TakeOutParam(2, out int x2)) {}

while (H.TakeOutParam(3, out int x3)) {}
object x3;

while (H.Dummy(H.TakeOutParam(41, out int x4),
               H.TakeOutParam(42, out int x4))) {}

while (H.TakeOutParam(51, out int x5)) 
{
    H.TakeOutParam(""52"", out string x5);
    H.Dummy(x5);
}
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,9): error CS0103: The name 'x1' does not exist in the current context
                // H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                // (12,43): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //                H.TakeOutParam(42, out int x4))) {}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 43),
                // (16,37): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     H.TakeOutParam("52", out string x5);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 37),
                // (19,9): error CS0103: The name 'x5' does not exist in the current context
                // H.Dummy(x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(19, 9),
                // (23,13): error CS0103: The name 'x1' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(23, 13),
                // (23,25): error CS0103: The name 'x4' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(23, 25),
                // (23,29): error CS0103: The name 'x5' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(23, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                    // (6,34): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // while (H.TakeOutParam(2, out int x2)) {}
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(6, 34),
                    // (8,34): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // while (H.TakeOutParam(3, out int x3)) {}
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(8, 34),
                    // (12,43): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                H.TakeOutParam(42, out int x4))) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 43),
                    // (16,37): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out string x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 37),
                    // (19,9): error CS0103: The name 'x5' does not exist in the current context
                    // H.Dummy(x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(19, 9),
                    // (21,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(21, 6),
                    // (23,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(23, 13),
                    // (23,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(23, 25),
                    // (23,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(23, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }
        }

        [Fact]
        public void GlobalCode_WhileStatement_02()
        {
            string source =
@"
while (H.TakeOutParam(1, out var x1)) {}
H.Dummy(x1);

object x2;
while (H.TakeOutParam(2, out var x2)) {}

while (H.TakeOutParam(3, out var x3)) {}
object x3;

while (H.Dummy(H.TakeOutParam(41, out var x4),
               H.TakeOutParam(42, out var x4))) {}

while (H.TakeOutParam(51, out var x5)) 
{
    H.TakeOutParam(""52"", out var x5);
    H.Dummy(x5);
}
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,9): error CS0103: The name 'x1' does not exist in the current context
                // H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                // (12,43): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //                H.TakeOutParam(42, out var x4))) {}
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 43),
                // (16,34): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     H.TakeOutParam("52", out var x5);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 34),
                // (19,9): error CS0103: The name 'x5' does not exist in the current context
                // H.Dummy(x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(19, 9),
                // (23,13): error CS0103: The name 'x1' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(23, 13),
                // (23,25): error CS0103: The name 'x4' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(23, 25),
                // (23,29): error CS0103: The name 'x5' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(23, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                    // (6,34): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // while (H.TakeOutParam(2, out var x2)) {}
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(6, 34),
                    // (8,34): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // while (H.TakeOutParam(3, out var x3)) {}
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(8, 34),
                    // (12,43): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                H.TakeOutParam(42, out var x4))) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 43),
                    // (16,34): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out var x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 34),
                    // (19,9): error CS0103: The name 'x5' does not exist in the current context
                    // H.Dummy(x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(19, 9),
                    // (21,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(21, 6),
                    // (23,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(23, 13),
                    // (23,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(23, 25),
                    // (23,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(23, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }
        }

        [Fact]
        public void GlobalCode_WhileStatement_03()
        {
            string source =
@"
while (H.TakeOutParam(1, out var x1)) 
{
    System.Console.WriteLine(x1);
    break;
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput: @"1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void GlobalCode_DoStatement_01()
        {
            string source =
@"
do {} while (H.TakeOutParam(1, out int x1));
H.Dummy(x1);

object x2;
do {} while (H.TakeOutParam(2, out int x2));

do {} while (H.TakeOutParam(3, out int x3));
object x3;

do {} while (H.Dummy(H.TakeOutParam(41, out int x4),
                     H.TakeOutParam(42, out int x4)));

do 
{
    H.TakeOutParam(""52"", out string x5);
    H.Dummy(x5);
}
while (H.TakeOutParam(51, out int x5));
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,9): error CS0103: The name 'x1' does not exist in the current context
                // H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                // (12,49): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //                      H.TakeOutParam(42, out int x4)));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 49),
                // (16,37): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     H.TakeOutParam("52", out string x5);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 37),
                // (20,9): error CS0103: The name 'x5' does not exist in the current context
                // H.Dummy(x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(20, 9),
                // (24,13): error CS0103: The name 'x1' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(24, 13),
                // (24,25): error CS0103: The name 'x4' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(24, 25),
                // (24,29): error CS0103: The name 'x5' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(24, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[0]);
                VerifyModelForOutVar(model, x5Decl[1]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                    // (6,40): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // do {} while (H.TakeOutParam(2, out int x2));
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(6, 40),
                    // (8,40): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // do {} while (H.TakeOutParam(3, out int x3));
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(8, 40),
                    // (12,49): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                      H.TakeOutParam(42, out int x4)));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 49),
                    // (16,37): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out string x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 37),
                    // (20,9): error CS0103: The name 'x5' does not exist in the current context
                    // H.Dummy(x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(20, 9),
                    // (22,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(22, 6),
                    // (24,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(24, 13),
                    // (24,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(24, 25),
                    // (24,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(24, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[0]);
                VerifyModelForOutVar(model, x5Decl[1]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }
        }

        [Fact]
        public void GlobalCode_DoStatement_02()
        {
            string source =
@"
do {} while (H.TakeOutParam(1, out var x1));
H.Dummy(x1);

object x2;
do {} while (H.TakeOutParam(2, out var x2));

do {} while (H.TakeOutParam(3, out var x3));
object x3;

do {} while (H.Dummy(H.TakeOutParam(41, out var x4),
                     H.TakeOutParam(42, out var x4)));

do 
{
    H.TakeOutParam(""52"", out var x5);
    H.Dummy(x5);
}
while (H.TakeOutParam(51, out var x5));
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,9): error CS0103: The name 'x1' does not exist in the current context
                // H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                // (12,49): error CS0128: A local variable or function named 'x4' is already defined in this scope
                //                      H.TakeOutParam(42, out var x4)));
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 49),
                // (16,34): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //     H.TakeOutParam("52", out var x5);
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 34),
                // (20,9): error CS0103: The name 'x5' does not exist in the current context
                // H.Dummy(x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(20, 9),
                // (24,13): error CS0103: The name 'x1' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(24, 13),
                // (24,25): error CS0103: The name 'x4' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(24, 25),
                // (24,29): error CS0103: The name 'x5' does not exist in the current context
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(24, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[0]);
                VerifyModelForOutVar(model, x5Decl[1]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(3, 9),
                    // (6,40): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // do {} while (H.TakeOutParam(2, out var x2));
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(6, 40),
                    // (8,40): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    // do {} while (H.TakeOutParam(3, out var x3));
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(8, 40),
                    // (12,49): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                      H.TakeOutParam(42, out var x4)));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 49),
                    // (16,34): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out var x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 34),
                    // (20,9): error CS0103: The name 'x5' does not exist in the current context
                    // H.Dummy(x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(20, 9),
                    // (22,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(22, 6),
                    // (24,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(24, 13),
                    // (24,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(24, 25),
                    // (24,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(24, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[0]);
                VerifyModelForOutVar(model, x5Decl[1]);
                VerifyNotInScope(model, x5Ref[1]);
                VerifyNotInScope(model, x5Ref[2]);
            }
        }

        [Fact]
        public void GlobalCode_DoStatement_03()
        {
            string source =
@"
int f = 1;

do
{
}
while (H.TakeOutParam(f++, out var x1) && Test(x1) < 3);

int Test(int x)
{
    System.Console.WriteLine(x);
    return x;
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"1
2
3").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Decl.Length);
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutVar(model, x1Decl[0], x1Ref);
        }

        [Fact]
        public void GlobalCode_LockStatement_01()
        {
            string source =
@"
lock (H.TakeOutParam(1, out int x1)) {}
H.Dummy(x1);

object x2;
lock (H.TakeOutParam(2, out int x2)) {}

lock (H.TakeOutParam(3, out int x3)) {}
object x3;

lock (H.Dummy(H.TakeOutParam(41, out int x4),
              H.TakeOutParam(42, out int x4))) {}

lock (H.TakeOutParam(51, out int x5)) 
{
    H.TakeOutParam(""52"", out string x5);
    H.Dummy(x5);
}
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static object Dummy(params object[] x) {return true;}
    public static object TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,33): error CS0102: The type 'Script' already contains a definition for 'x2'
                // lock (H.TakeOutParam(2, out int x2)) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 33),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,42): error CS0102: The type 'Script' already contains a definition for 'x4'
                //               H.TakeOutParam(42, out int x4))) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 42),
                // (23,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(23, 17),
                // (23,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(23, 21),
                // (23,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(23, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,33): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // lock (H.TakeOutParam(2, out int x2)) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 33),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,42): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //               H.TakeOutParam(42, out int x4))) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 42),
                    // (16,37): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out string x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 37),
                    // (26,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(26, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }
        }

        [Fact]
        public void GlobalCode_LockStatement_02()
        {
            string source =
@"
lock (H.TakeOutParam(1, out var x1)) {}
H.Dummy(x1);

object x2;
lock (H.TakeOutParam(2, out var x2)) {}

lock (H.TakeOutParam(3, out var x3)) {}
object x3;

lock (H.Dummy(H.TakeOutParam(41, out var x4),
              H.TakeOutParam(42, out var x4))) {}

lock (H.TakeOutParam(51, out var x5)) 
{
    H.TakeOutParam(""52"", out var x5);
    H.Dummy(x5);
}
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static object Dummy(params object[] x) {return true;}
    public static object TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,33): error CS0102: The type 'Script' already contains a definition for 'x2'
                // lock (H.TakeOutParam(2, out var x2)) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 33),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,42): error CS0102: The type 'Script' already contains a definition for 'x4'
                //               H.TakeOutParam(42, out var x4))) {}
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 42),
                // (23,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(23, 17),
                // (23,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(23, 21),
                // (23,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(23, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,33): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // lock (H.TakeOutParam(2, out var x2)) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 33),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,42): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //               H.TakeOutParam(42, out var x4))) {}
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 42),
                    // (16,34): error CS0136: A local or parameter named 'x5' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                    //     H.TakeOutParam("52", out var x5);
                    Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x5").WithArguments("x5").WithLocation(16, 34),
                    // (26,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(26, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Decl.Length);
                Assert.Equal(3, x5Ref.Length);
                VerifyModelForOutVar(model, x5Decl[0], x5Ref[1], x5Ref[2]);
                VerifyModelForOutVar(model, x5Decl[1], x5Ref[0]);
            }
        }

        [Fact]
        public void GlobalCode_LockStatement_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
lock (H.TakeOutParam(1, out var x1)) 
{
    H.TakeOutParam(""11"", out var x1);
    System.Console.WriteLine(x1);
}
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static object TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
11
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        public void GlobalCode_LockStatement_04()
        {
            string source =
@"
System.Console.WriteLine(x1);
lock (H.TakeOutParam(1, out var x1)) 
    H.Dummy(H.TakeOutParam(""11"", out var x1), x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static void Dummy(object x, object y)
    {
        System.Console.WriteLine(y);
    }

    public static object TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
11
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Decl.Length);
            Assert.Equal(3, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl[0], x1Ref[0], x1Ref[2]);
            VerifyModelForOutVar(model, x1Decl[1], x1Ref[1]);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void GlobalCode_DeconstructionDeclarationStatement_01()
        {
            string source =
@"
(bool a, int b) = (H.TakeOutParam(1, out int x1), 1);
H.Dummy(x1);

object x2;
(bool c, int d) = (H.TakeOutParam(2, out int x2), 2);

(bool e, int f) = (H.TakeOutParam(3, out int x3), 3);
object x3;

(bool g, bool h) = (H.TakeOutParam(41, out int x4),
                    H.TakeOutParam(42, out int x4));

(bool x5, bool x6) = (H.TakeOutParam(5, out int x5),
                      H.TakeOutParam(6, out int x6));
Test();
void Test()
{
    H.Dummy(x1, x2, x3, x4, x5, x6);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                                  options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,46): error CS0102: The type 'Script' already contains a definition for 'x2'
                // (bool c, int d) = (H.TakeOutParam(2, out int x2), 2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 46),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,48): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                     H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 48),
                // (14,49): error CS0102: The type 'Script' already contains a definition for 'x5'
                // (bool x5, bool x6) = (H.TakeOutParam(5, out int x5),
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(14, 49),
                // (15,49): error CS0102: The type 'Script' already contains a definition for 'x6'
                //                       H.TakeOutParam(6, out int x6));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x6").WithArguments("Script", "x6").WithLocation(15, 49),
                // (19,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(19, 17),
                // (19,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(19, 21),
                // (19,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(19, 25),
                // (19,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(19, 29),
                // (19,33): error CS0229: Ambiguity between 'x6' and 'x6'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x6").WithArguments("x6", "x6").WithLocation(19, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(1, x5Ref.Length);
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref[0]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(1, x6Ref.Length);
                VerifyModelForOutFieldDuplicate(model, x6Decl, x6Ref[0]);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                                  options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (6,46): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // (bool c, int d) = (H.TakeOutParam(2, out int x2), 2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 46),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (12,48): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                     H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 48),
                    // (14,49): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    // (bool x5, bool x6) = (H.TakeOutParam(5, out int x5),
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(14, 49),
                    // (15,49): error CS0128: A local variable or function named 'x6' is already defined in this scope
                    //                       H.TakeOutParam(6, out int x6));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(15, 49),
                    // (16,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(16, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(1, x5Ref.Length);
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl);
                VerifyNotAnOutLocal(model, x5Ref[0]);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(1, x6Ref.Length);
                VerifyModelForOutVarDuplicateInSameScope(model, x6Decl);
                VerifyNotAnOutLocal(model, x6Ref[0]);
            }
        }

        [Fact]
        public void GlobalCode_LabeledStatement_01()
        {
            string source =
@"
a: H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
b: H.TakeOutParam(2, out int x2);

c: H.TakeOutParam(3, out int x3);
object x3;

d: H.Dummy(H.TakeOutParam(41, out int x4),
           H.TakeOutParam(42, out int x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,30): error CS0102: The type 'Script' already contains a definition for 'x2'
                // b: H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 30),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,39): error CS0102: The type 'Script' already contains a definition for 'x4'
                //            H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 39),
                // (2,1): warning CS0164: This label has not been referenced
                // a: H.TakeOutParam(1, out int x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                // (6,1): warning CS0164: This label has not been referenced
                // b: H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(6, 1),
                // (8,1): warning CS0164: This label has not been referenced
                // c: H.TakeOutParam(3, out int x3);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(8, 1),
                // (11,1): warning CS0164: This label has not been referenced
                // d: H.Dummy(H.TakeOutParam(41, out int x4),
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "d").WithLocation(11, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,1): warning CS0164: This label has not been referenced
                    // a: H.TakeOutParam(1, out int x1);
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                    // (6,1): warning CS0164: This label has not been referenced
                    // b: H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(6, 1),
                    // (6,30): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // b: H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 30),
                    // (8,1): warning CS0164: This label has not been referenced
                    // c: H.TakeOutParam(3, out int x3);
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(8, 1),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (11,1): warning CS0164: This label has not been referenced
                    // d: H.Dummy(H.TakeOutParam(41, out int x4),
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "d").WithLocation(11, 1),
                    // (12,39): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //            H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 39),
                    // (19,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(19, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_LabeledStatement_02()
        {
            string source =
@"
a: H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
b: H.TakeOutParam(2, out var x2);

c: H.TakeOutParam(3, out var x3);
object x3;

d: H.Dummy(H.TakeOutParam(41, out var x4),
           H.TakeOutParam(42, out var x4));

void Test()
{
    H.Dummy(x1, x2, x3, x4);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,30): error CS0102: The type 'Script' already contains a definition for 'x2'
                // b: H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 30),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,39): error CS0102: The type 'Script' already contains a definition for 'x4'
                //            H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 39),
                // (2,1): warning CS0164: This label has not been referenced
                // a: H.TakeOutParam(1, out var x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                // (6,1): warning CS0164: This label has not been referenced
                // b: H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(6, 1),
                // (8,1): warning CS0164: This label has not been referenced
                // c: H.TakeOutParam(3, out var x3);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(8, 1),
                // (11,1): warning CS0164: This label has not been referenced
                // d: H.Dummy(H.TakeOutParam(41, out var x4),
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "d").WithLocation(11, 1),
                // (16,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(16, 17),
                // (16,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(16, 21),
                // (16,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(16, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,1): warning CS0164: This label has not been referenced
                    // a: H.TakeOutParam(1, out var x1);
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                    // (6,1): warning CS0164: This label has not been referenced
                    // b: H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(6, 1),
                    // (6,30): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // b: H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 30),
                    // (8,1): warning CS0164: This label has not been referenced
                    // c: H.TakeOutParam(3, out var x3);
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(8, 1),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (11,1): warning CS0164: This label has not been referenced
                    // d: H.Dummy(H.TakeOutParam(41, out var x4),
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "d").WithLocation(11, 1),
                    // (12,39): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //            H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 39),
                    // (19,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(19, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
            }
        }

        [Fact]
        public void GlobalCode_LabeledStatement_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
a:b:c:H.TakeOutParam(1, out var x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
1").VerifyDiagnostics(
                // (3,1): warning CS0164: This label has not been referenced
                // a:b:c:H.TakeOutParam(1, out var x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(3, 1),
                // (3,3): warning CS0164: This label has not been referenced
                // a:b:c:H.TakeOutParam(1, out var x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(3, 3),
                // (3,5): warning CS0164: This label has not been referenced
                // a:b:c:H.TakeOutParam(1, out var x1);
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(3, 5)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_LabeledStatement_04()
        {
            string source =
@"
a: 
bool b = H.TakeOutParam(1, out int x1);
H.Dummy(x1);
object x2;
c:
bool d = H.TakeOutParam(2, out int x2);
e:
bool f = H.TakeOutParam(3, out int x3);
object x3;
g:
bool h = H.Dummy(H.TakeOutParam(41, out int x4),
                 H.TakeOutParam(42, out int x4));
i:
bool x5 = H.TakeOutParam(5, out int x5);
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,36): error CS0102: The type 'Script' already contains a definition for 'x2'
                // bool d = H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 36),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,45): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                  H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 45),
                // (2,1): warning CS0164: This label has not been referenced
                // a: 
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                // (6,1): warning CS0164: This label has not been referenced
                // c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(6, 1),
                // (8,1): warning CS0164: This label has not been referenced
                // e:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "e").WithLocation(8, 1),
                // (11,1): warning CS0164: This label has not been referenced
                // g:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "g").WithLocation(11, 1),
                // (14,1): warning CS0164: This label has not been referenced
                // i:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "i").WithLocation(14, 1),
                // (20,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(20, 17),
                // (20,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(20, 21),
                // (20,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(20, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl, x5Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,1): warning CS0164: This label has not been referenced
                    // a: 
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                    // (6,1): warning CS0164: This label has not been referenced
                    // c:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(6, 1),
                    // (7,36): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // bool d = H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(7, 36),
                    // (8,1): warning CS0164: This label has not been referenced
                    // e:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "e").WithLocation(8, 1),
                    // (10,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (10,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (11,1): warning CS0164: This label has not been referenced
                    // g:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "g").WithLocation(11, 1),
                    // (13,45): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                  H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 45),
                    // (14,1): warning CS0164: This label has not been referenced
                    // i:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "i").WithLocation(14, 1),
                    // (15,37): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    // bool x5 = H.TakeOutParam(5, out int x5);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(15, 37),
                    // (23,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(23, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Ref.Length);
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl);
                VerifyNotAnOutLocal(model, x5Ref[0]);
                VerifyNotAnOutLocal(model, x5Ref[1]);
            }
        }

        [Fact]
        public void GlobalCode_LabeledStatement_05()
        {
            string source =
@"
a: 
bool b = H.TakeOutParam(1, out var x1);
H.Dummy(x1);
object x2;
c:
bool d = H.TakeOutParam(2, out var x2);
e:
bool f = H.TakeOutParam(3, out var x3);
object x3;
g:
bool h = H.Dummy(H.TakeOutParam(41, out var x4),
                 H.TakeOutParam(42, out var x4));
i:
bool x5 = H.TakeOutParam(5, out var x5);
H.Dummy(x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,36): error CS0102: The type 'Script' already contains a definition for 'x2'
                // bool d = H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 36),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,45): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                  H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 45),
                // (2,1): warning CS0164: This label has not been referenced
                // a: 
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                // (6,1): warning CS0164: This label has not been referenced
                // c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(6, 1),
                // (8,1): warning CS0164: This label has not been referenced
                // e:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "e").WithLocation(8, 1),
                // (11,1): warning CS0164: This label has not been referenced
                // g:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "g").WithLocation(11, 1),
                // (14,1): warning CS0164: This label has not been referenced
                // i:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "i").WithLocation(14, 1),
                // (20,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(20, 17),
                // (20,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(20, 21),
                // (20,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(20, 25)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Ref.Length);
                VerifyModelForOutField(model, x5Decl, x5Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (2,1): warning CS0164: This label has not been referenced
                    // a: 
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(2, 1),
                    // (6,1): warning CS0164: This label has not been referenced
                    // c:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(6, 1),
                    // (7,36): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // bool d = H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(7, 36),
                    // (8,1): warning CS0164: This label has not been referenced
                    // e:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "e").WithLocation(8, 1),
                    // (10,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (10,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (11,1): warning CS0164: This label has not been referenced
                    // g:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "g").WithLocation(11, 1),
                    // (13,45): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                  H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 45),
                    // (14,1): warning CS0164: This label has not been referenced
                    // i:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "i").WithLocation(14, 1),
                    // (15,37): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    // bool x5 = H.TakeOutParam(5, out var x5);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(15, 37),
                    // (23,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(23, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(2, x5Ref.Length);
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl);
                VerifyNotAnOutLocal(model, x5Ref[0]);
                VerifyNotAnOutLocal(model, x5Ref[1]);
            }
        }

        [ConditionalFact(typeof(IsRelease), Reason = "https://github.com/dotnet/roslyn/issues/25702")]
        public void GlobalCode_LabeledStatement_06_Script()
        {
            string source =
@"
System.Console.WriteLine(x1);
a:b:c:
var d = H.TakeOutParam(1, out var x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
1").VerifyDiagnostics(
                // (3,1): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(3, 1),
                // (3,3): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(3, 3),
                // (3,5): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(3, 5)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_LabeledStatement_06_SimpleProgram()
        {
            string source =
@"

a:b:c:
var d = H.TakeOutParam(1, out var x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular9);

            CompileAndVerify(compilation, expectedOutput:
@"1").VerifyDiagnostics(
                // (3,1): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(3, 1),
                // (3,3): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(3, 3),
                // (3,5): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(3, 5)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutVar(model, x1Decl, x1Ref);
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void GlobalCode_LabeledStatement_07()
        {
            string source =
@"l1:
(bool a, int b) = (H.TakeOutParam(1, out int x1), 1);
H.Dummy(x1);
object x2;
l2:
(bool c, int d) = (H.TakeOutParam(2, out int x2), 2);
l3:
(bool e, int f) = (H.TakeOutParam(3, out int x3), 3);
object x3;
l4:
(bool g, bool h) = (H.TakeOutParam(41, out int x4),
                    H.TakeOutParam(42, out int x4));
l5:
(bool x5, bool x6) = (H.TakeOutParam(5, out int x5),
                      H.TakeOutParam(6, out int x6));

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5, x6);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                                  options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,46): error CS0102: The type 'Script' already contains a definition for 'x2'
                // (bool c, int d) = (H.TakeOutParam(2, out int x2), 2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 46),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,48): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                     H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 48),
                // (14,49): error CS0102: The type 'Script' already contains a definition for 'x5'
                // (bool x5, bool x6) = (H.TakeOutParam(5, out int x5),
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(14, 49),
                // (15,49): error CS0102: The type 'Script' already contains a definition for 'x6'
                //                       H.TakeOutParam(6, out int x6));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x6").WithArguments("Script", "x6").WithLocation(15, 49),
                // (1,1): warning CS0164: This label has not been referenced
                // l1:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l1").WithLocation(1, 1),
                // (5,1): warning CS0164: This label has not been referenced
                // l2:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l2").WithLocation(5, 1),
                // (7,1): warning CS0164: This label has not been referenced
                // l3:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l3").WithLocation(7, 1),
                // (10,1): warning CS0164: This label has not been referenced
                // l4:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l4").WithLocation(10, 1),
                // (13,1): warning CS0164: This label has not been referenced
                // l5:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l5").WithLocation(13, 1),
                // (19,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(19, 17),
                // (19,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(19, 21),
                // (19,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(19, 25),
                // (19,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(19, 29),
                // (19,33): error CS0229: Ambiguity between 'x6' and 'x6'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x6").WithArguments("x6", "x6").WithLocation(19, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(1, x5Ref.Length);
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(1, x6Ref.Length);
                VerifyModelForOutFieldDuplicate(model, x6Decl, x6Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                                  options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (1,1): warning CS0164: This label has not been referenced
                    // l1:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l1").WithLocation(1, 1),
                    // (5,1): warning CS0164: This label has not been referenced
                    // l2:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l2").WithLocation(5, 1),
                    // (6,46): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // (bool c, int d) = (H.TakeOutParam(2, out int x2), 2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 46),
                    // (7,1): warning CS0164: This label has not been referenced
                    // l3:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l3").WithLocation(7, 1),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (10,1): warning CS0164: This label has not been referenced
                    // l4:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l4").WithLocation(10, 1),
                    // (12,48): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                     H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 48),
                    // (13,1): warning CS0164: This label has not been referenced
                    // l5:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l5").WithLocation(13, 1),
                    // (14,49): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    // (bool x5, bool x6) = (H.TakeOutParam(5, out int x5),
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(14, 49),
                    // (15,49): error CS0128: A local variable or function named 'x6' is already defined in this scope
                    //                       H.TakeOutParam(6, out int x6));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(15, 49),
                    // (22,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(22, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl);
                VerifyNotAnOutLocal(model, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x6Decl);
                VerifyNotAnOutLocal(model, x6Ref);
            }
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void GlobalCode_LabeledStatement_08()
        {
            string source =
@"l1:
(bool a, int b) = (H.TakeOutParam(1, out var x1), 1);
H.Dummy(x1);
object x2;
l2:
(bool c, int d) = (H.TakeOutParam(2, out var x2), 2);
l3:
(bool e, int f) = (H.TakeOutParam(3, out var x3), 3);
object x3;
l4:
(bool g, bool h) = (H.TakeOutParam(41, out var x4),
                    H.TakeOutParam(42, out var x4));
l5:
(bool x5, bool x6) = (H.TakeOutParam(5, out var x5),
                      H.TakeOutParam(6, out var x6));

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5, x6);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                                  options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (6,46): error CS0102: The type 'Script' already contains a definition for 'x2'
                // (bool c, int d) = (H.TakeOutParam(2, out var x2), 2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(6, 46),
                // (9,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(9, 8),
                // (12,48): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                     H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(12, 48),
                // (14,49): error CS0102: The type 'Script' already contains a definition for 'x5'
                // (bool x5, bool x6) = (H.TakeOutParam(5, out var x5),
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(14, 49),
                // (15,49): error CS0102: The type 'Script' already contains a definition for 'x6'
                //                       H.TakeOutParam(6, out var x6));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x6").WithArguments("Script", "x6").WithLocation(15, 49),
                // (1,1): warning CS0164: This label has not been referenced
                // l1:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l1").WithLocation(1, 1),
                // (5,1): warning CS0164: This label has not been referenced
                // l2:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l2").WithLocation(5, 1),
                // (7,1): warning CS0164: This label has not been referenced
                // l3:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l3").WithLocation(7, 1),
                // (10,1): warning CS0164: This label has not been referenced
                // l4:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l4").WithLocation(10, 1),
                // (13,1): warning CS0164: This label has not been referenced
                // l5:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l5").WithLocation(13, 1),
                // (19,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(19, 17),
                // (19,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(19, 21),
                // (19,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(19, 25),
                // (19,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(19, 29),
                // (19,33): error CS0229: Ambiguity between 'x6' and 'x6'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x6").WithArguments("x6", "x6").WithLocation(19, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").ToArray();
                Assert.Equal(1, x5Ref.Length);
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").ToArray();
                Assert.Equal(1, x6Ref.Length);
                VerifyModelForOutFieldDuplicate(model, x6Decl, x6Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                                  options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (1,1): warning CS0164: This label has not been referenced
                    // l1:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l1").WithLocation(1, 1),
                    // (5,1): warning CS0164: This label has not been referenced
                    // l2:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l2").WithLocation(5, 1),
                    // (6,46): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // (bool c, int d) = (H.TakeOutParam(2, out var x2), 2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(6, 46),
                    // (7,1): warning CS0164: This label has not been referenced
                    // l3:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l3").WithLocation(7, 1),
                    // (9,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (9,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(9, 8),
                    // (10,1): warning CS0164: This label has not been referenced
                    // l4:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l4").WithLocation(10, 1),
                    // (12,48): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                     H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(12, 48),
                    // (13,1): warning CS0164: This label has not been referenced
                    // l5:
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "l5").WithLocation(13, 1),
                    // (14,49): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    // (bool x5, bool x6) = (H.TakeOutParam(5, out var x5),
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(14, 49),
                    // (15,49): error CS0128: A local variable or function named 'x6' is already defined in this scope
                    //                       H.TakeOutParam(6, out var x6));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(15, 49),
                    // (22,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(22, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl);
                VerifyNotAnOutLocal(model, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x6Decl);
                VerifyNotAnOutLocal(model, x6Ref);
            }
        }

        [Fact]
        [CompilerTrait(CompilerFeature.Tuples)]
        public void GlobalCode_LabeledStatement_09()
        {
            string source =
@"
System.Console.WriteLine(x1);
a:b:c:
var (d, e) = (H.TakeOutParam(1, out var x1), 1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, references: new[] { ValueTupleRef, SystemRuntimeFacadeRef },
                                                              options: TestOptions.DebugExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
1").VerifyDiagnostics(
                // (3,1): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "a").WithLocation(3, 1),
                // (3,3): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "b").WithLocation(3, 3),
                // (3,5): warning CS0164: This label has not been referenced
                // a:b:c:
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "c").WithLocation(3, 5)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_FieldDeclaration_01()
        {
            string source =
@"
 
bool b = H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
bool d = H.TakeOutParam(2, out int x2);

bool f = H.TakeOutParam(3, out int x3);
object x3;

bool h = H.Dummy(H.TakeOutParam(41, out int x4),
                 H.TakeOutParam(42, out int x4));

bool x5 = 
          H.TakeOutParam(5, out int x5);

bool i = H.TakeOutParam(5, out int x6),
         x6;

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5, x6);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,36): error CS0102: The type 'Script' already contains a definition for 'x2'
                // bool d = H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 36),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,45): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                  H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 45),
                // (16,37): error CS0102: The type 'Script' already contains a definition for 'x5'
                //           H.TakeOutParam(5, out int x5);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(16, 37),
                // (19,10): error CS0102: The type 'Script' already contains a definition for 'x6'
                //          x6;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x6").WithArguments("Script", "x6").WithLocation(19, 10),
                // (23,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(23, 17),
                // (23,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(23, 21),
                // (23,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(23, 25),
                // (23,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(23, 29),
                // (23,33): error CS0229: Ambiguity between 'x6' and 'x6'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x6").WithArguments("x6", "x6").WithLocation(23, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutFieldDuplicate(model, x6Decl, x6Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (7,36): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // bool d = H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(7, 36),
                    // (10,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (10,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (13,45): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                  H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 45),
                    // (16,37): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    //           H.TakeOutParam(5, out int x5);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(16, 37),
                    // (19,10): error CS0128: A local variable or function named 'x6' is already defined in this scope
                    //          x6;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(19, 10),
                    // (19,10): warning CS0168: The variable 'x6' is declared but never used
                    //          x6;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x6").WithArguments("x6").WithLocation(19, 10),
                    // (26,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(26, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl);
                VerifyNotAnOutLocal(model, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutVar(model, x6Decl, x6Ref);
            }
        }

        [Fact]
        public void GlobalCode_FieldDeclaration_02()
        {
            string source =
@"
 
bool b = H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
bool d = H.TakeOutParam(2, out var x2);

bool f = H.TakeOutParam(3, out var x3);
object x3;

bool h = H.Dummy(H.TakeOutParam(41, out var x4),
                 H.TakeOutParam(42, out var x4));

bool x5 = 
          H.TakeOutParam(5, out var x5);

bool i = H.TakeOutParam(5, out var x6),
         x6;

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5, x6);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,36): error CS0102: The type 'Script' already contains a definition for 'x2'
                // bool d = H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 36),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,45): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                  H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 45),
                // (16,37): error CS0102: The type 'Script' already contains a definition for 'x5'
                //           H.TakeOutParam(5, out var x5);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(16, 37),
                // (19,10): error CS0102: The type 'Script' already contains a definition for 'x6'
                //          x6;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x6").WithArguments("Script", "x6").WithLocation(19, 10),
                // (23,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(23, 17),
                // (23,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(23, 21),
                // (23,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(23, 25),
                // (23,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(23, 29),
                // (23,33): error CS0229: Ambiguity between 'x6' and 'x6'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x6").WithArguments("x6", "x6").WithLocation(23, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutFieldDuplicate(model, x6Decl, x6Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (7,36): error CS0128: A local variable or function named 'x2' is already defined in this scope
                    // bool d = H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(7, 36),
                    // (10,8): error CS0128: A local variable or function named 'x3' is already defined in this scope
                    // object x3;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (10,8): warning CS0168: The variable 'x3' is declared but never used
                    // object x3;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x3").WithArguments("x3").WithLocation(10, 8),
                    // (13,45): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                  H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 45),
                    // (16,37): error CS0128: A local variable or function named 'x5' is already defined in this scope
                    //           H.TakeOutParam(5, out var x5);
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(16, 37),
                    // (19,10): error CS0128: A local variable or function named 'x6' is already defined in this scope
                    //          x6;
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(19, 10),
                    // (19,10): warning CS0168: The variable 'x6' is declared but never used
                    //          x6;
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "x6").WithArguments("x6").WithLocation(19, 10),
                    // (26,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(26, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0], x4Ref);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVarDuplicateInSameScope(model, x5Decl);
                VerifyNotAnOutLocal(model, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutVar(model, x6Decl, x6Ref);
            }
        }

        [Fact]
        public void GlobalCode_FieldDeclaration_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
var d = H.TakeOutParam(1, out var x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_FieldDeclaration_04()
        {
            string source =
@"
static var a = InitA();
System.Console.WriteLine(x1);
static var b = H.TakeOutParam(1, out var x1);
Test();
static var c = InitB();

void Test()
{
    System.Console.WriteLine(x1);
}

static object InitA()
{
    System.Console.WriteLine(""InitA {0}"", x1);
    return null;
}

static object InitB()
{
    System.Console.WriteLine(""InitB {0}"", x1);
    return null;
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"InitA 0
InitB 1
1
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(4, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_FieldDeclaration_05()
        {
            string source =
@"
 
bool b = H.TakeOutParam(1, out var x1);
static var d = x1;

static void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.VerifyDiagnostics(
                // (4,16): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                // static var d = x1;
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(4, 16),
                // (8,13): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                //     H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(8, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_FieldDeclaration_06()
        {
            string source =
@"
 
bool b = H.TakeOutParam(1, out int x1);
static var d = x1;

static void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.VerifyDiagnostics(
                // (4,16): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                // static var d = x1;
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(4, 16),
                // (8,13): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                //     H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(8, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_FieldDeclaration_07()
        {
            string source =
@"
Test();
bool a = H.TakeOutParam(1, out var x1), b = Test(), c = H.TakeOutParam(2, out var x2);
Test();

bool Test()
{
    System.Console.WriteLine(""{0} {1}"", x1, x2);
    return false;
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0 0
1 0
1 2").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutField(model, x2Decl, x2Ref);
        }

        [Fact]
        public void GlobalCode_PropertyDeclaration_01()
        {
            string source =
@"
 
bool b { get; } = H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
bool d { get; } = H.TakeOutParam(2, out int x2);

bool f { get; } = H.TakeOutParam(3, out int x3);
object x3;

bool h { get; } = H.Dummy(H.TakeOutParam(41, out int x4),
                          H.TakeOutParam(42, out int x4));

bool x5 { get; } = 
          H.TakeOutParam(5, out int x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,45): error CS0102: The type 'Script' already contains a definition for 'x2'
                // bool d { get; } = H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 45),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,54): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                           H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 54),
                // (16,37): error CS0102: The type 'Script' already contains a definition for 'x5'
                //           H.TakeOutParam(5, out int x5);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(16, 37),
                // (20,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(20, 17),
                // (20,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(20, 21),
                // (20,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(20, 25),
                // (20,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(20, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool b { get; } = H.TakeOutParam(1, out int x1);
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "b").WithLocation(3, 6),
                    // (4,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(4, 9),
                    // (7,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool d { get; } = H.TakeOutParam(2, out int x2);
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "d").WithLocation(7, 6),
                    // (9,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool f { get; } = H.TakeOutParam(3, out int x3);
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "f").WithLocation(9, 6),
                    // (12,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool h { get; } = H.Dummy(H.TakeOutParam(41, out int x4),
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "h").WithLocation(12, 6),
                    // (13,54): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                           H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 54),
                    // (15,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool x5 { get; } = 
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "x5").WithLocation(15, 6),
                    // (20,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(20, 13),
                    // (20,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(20, 25),
                    // (20,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(20, 29),
                    // (23,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(23, 1),
                    // (23,1): error CS0165: Use of unassigned local variable 'x3'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x3").WithLocation(23, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVar(model, x5Decl);
                VerifyNotInScope(model, x5Ref);
            }
        }

        [Fact]
        public void GlobalCode_PropertyDeclaration_02()
        {
            string source =
@"
 
bool b { get; } = H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
bool d { get; } = H.TakeOutParam(2, out var x2);

bool f { get; } = H.TakeOutParam(3, out var x3);
object x3;

bool h { get; } = H.Dummy(H.TakeOutParam(41, out var x4),
                          H.TakeOutParam(42, out var x4));

bool x5 { get; } = 
          H.TakeOutParam(5, out var x5);

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5);
}

Test();

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,45): error CS0102: The type 'Script' already contains a definition for 'x2'
                // bool d { get; } = H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 45),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,54): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                           H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 54),
                // (16,37): error CS0102: The type 'Script' already contains a definition for 'x5'
                //           H.TakeOutParam(5, out var x5);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(16, 37),
                // (20,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(20, 17),
                // (20,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(20, 21),
                // (20,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(20, 25),
                // (20,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(20, 29)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool b { get; } = H.TakeOutParam(1, out var x1);
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "b").WithLocation(3, 6),
                    // (4,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(4, 9),
                    // (7,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool d { get; } = H.TakeOutParam(2, out var x2);
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "d").WithLocation(7, 6),
                    // (9,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool f { get; } = H.TakeOutParam(3, out var x3);
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "f").WithLocation(9, 6),
                    // (12,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool h { get; } = H.Dummy(H.TakeOutParam(41, out var x4),
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "h").WithLocation(12, 6),
                    // (13,54): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                           H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 54),
                    // (15,6): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties
                    // bool x5 { get; } = 
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "x5").WithLocation(15, 6),
                    // (20,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(20, 13),
                    // (20,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(20, 25),
                    // (20,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(20, 29),
                    // (23,1): error CS0165: Use of unassigned local variable 'x2'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x2").WithLocation(23, 1),
                    // (23,1): error CS0165: Use of unassigned local variable 'x3'
                    // Test();
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "Test()").WithArguments("x3").WithLocation(23, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVar(model, x5Decl);
                VerifyNotInScope(model, x5Ref);
            }
        }

        [Fact]
        public void GlobalCode_PropertyDeclaration_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
bool d { get; set; } = H.TakeOutParam(1, out var x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_PropertyDeclaration_04()
        {
            string source =
@"
static var a = InitA();
System.Console.WriteLine(x1);
static bool b { get; } = H.TakeOutParam(1, out var x1);
Test();
static var c = InitB();

void Test()
{
    System.Console.WriteLine(x1);
}

static object InitA()
{
    System.Console.WriteLine(""InitA {0}"", x1);
    return null;
}

static object InitB()
{
    System.Console.WriteLine(""InitB {0}"", x1);
    return null;
}

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"InitA 0
InitB 1
1
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(4, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_PropertyDeclaration_05()
        {
            string source =
@"
 
bool b { get; } = H.TakeOutParam(1, out var x1);
static var d = x1;

static void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.VerifyDiagnostics(
                // (4,16): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                // static var d = x1;
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(4, 16),
                // (8,13): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                //     H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(8, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_PropertyDeclaration_06()
        {
            string source =
@"
 
bool b { get; } = H.TakeOutParam(1, out int x1);
static var d = x1;

static void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.VerifyDiagnostics(
                // (4,16): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                // static var d = x1;
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(4, 16),
                // (8,13): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                //     H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(8, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_EventDeclaration_01()
        {
            string source =
@"
 
event System.Action b = H.TakeOutParam(1, out int x1);
H.Dummy(x1);

object x2;
event System.Action d = H.TakeOutParam(2, out int x2);

event System.Action f = H.TakeOutParam(3, out int x3);
object x3;

event System.Action h = H.Dummy(H.TakeOutParam(41, out int x4),
                        H.TakeOutParam(42, out int x4));

event System.Action x5 = 
          H.TakeOutParam(5, out int x5);

event System.Action i = H.TakeOutParam(5, out int x6),
         x6;

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5, x6);
}

class H
{
    public static System.Action Dummy(params object[] x) {return null;}
    public static System.Action TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,51): error CS0102: The type 'Script' already contains a definition for 'x2'
                // event System.Action d = H.TakeOutParam(2, out int x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 51),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,52): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                         H.TakeOutParam(42, out int x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 52),
                // (16,37): error CS0102: The type 'Script' already contains a definition for 'x5'
                //           H.TakeOutParam(5, out int x5);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(16, 37),
                // (19,10): error CS0102: The type 'Script' already contains a definition for 'x6'
                //          x6;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x6").WithArguments("Script", "x6").WithLocation(19, 10),
                // (23,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(23, 17),
                // (23,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(23, 21),
                // (23,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(23, 25),
                // (23,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(23, 29),
                // (23,33): error CS0229: Ambiguity between 'x6' and 'x6'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x6").WithArguments("x6", "x6").WithLocation(23, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutFieldDuplicate(model, x6Decl, x6Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);
                int[] exclude = new int[] { (int)ErrorCode.ERR_CompilationUnitUnexpected };

                compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                    // (4,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(4, 9),
                    // (13,52): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                         H.TakeOutParam(42, out int x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 52),
                    // (21,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(21, 6),
                    // (23,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(23, 13),
                    // (23,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(23, 25),
                    // (23,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(23, 29),
                    // (23,33): error CS0103: The name 'x6' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x6").WithArguments("x6").WithLocation(23, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVar(model, x5Decl);
                VerifyNotInScope(model, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutVar(model, x6Decl);
                VerifyNotInScope(model, x6Ref);
            }
        }

        [Fact]
        public void GlobalCode_EventDeclaration_02()
        {
            string source =
@"
 
event System.Action b = H.TakeOutParam(1, out var x1);
H.Dummy(x1);

object x2;
event System.Action d = H.TakeOutParam(2, out var x2);

event System.Action f = H.TakeOutParam(3, out var x3);
object x3;

event System.Action h = H.Dummy(H.TakeOutParam(41, out var x4),
                        H.TakeOutParam(42, out var x4));

event System.Action x5 = 
          H.TakeOutParam(5, out var x5);

event System.Action i = H.TakeOutParam(5, out var x6),
         x6;

void Test()
{
    H.Dummy(x1, x2, x3, x4, x5, x6);
}

class H
{
    public static System.Action Dummy(params object[] x) {return null;}
    public static System.Action TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (7,51): error CS0102: The type 'Script' already contains a definition for 'x2'
                // event System.Action d = H.TakeOutParam(2, out var x2);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x2").WithArguments("Script", "x2").WithLocation(7, 51),
                // (10,8): error CS0102: The type 'Script' already contains a definition for 'x3'
                // object x3;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x3").WithArguments("Script", "x3").WithLocation(10, 8),
                // (13,52): error CS0102: The type 'Script' already contains a definition for 'x4'
                //                         H.TakeOutParam(42, out var x4));
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x4").WithArguments("Script", "x4").WithLocation(13, 52),
                // (16,37): error CS0102: The type 'Script' already contains a definition for 'x5'
                //           H.TakeOutParam(5, out var x5);
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x5").WithArguments("Script", "x5").WithLocation(16, 37),
                // (19,10): error CS0102: The type 'Script' already contains a definition for 'x6'
                //          x6;
                Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "x6").WithArguments("Script", "x6").WithLocation(19, 10),
                // (23,17): error CS0229: Ambiguity between 'x2' and 'x2'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x2").WithArguments("x2", "x2").WithLocation(23, 17),
                // (23,21): error CS0229: Ambiguity between 'x3' and 'x3'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x3").WithArguments("x3", "x3").WithLocation(23, 21),
                // (23,25): error CS0229: Ambiguity between 'x4' and 'x4'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x4").WithArguments("x4", "x4").WithLocation(23, 25),
                // (23,29): error CS0229: Ambiguity between 'x5' and 'x5'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x5").WithArguments("x5", "x5").WithLocation(23, 29),
                // (23,33): error CS0229: Ambiguity between 'x6' and 'x6'
                //     H.Dummy(x1, x2, x3, x4, x5, x6);
                Diagnostic(ErrorCode.ERR_AmbigMember, "x6").WithArguments("x6", "x6").WithLocation(23, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutField(model, x1Decl, x1Ref);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutFieldDuplicate(model, x2Decl, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutFieldDuplicate(model, x3Decl, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutFieldDuplicate(model, x4Decl[0], x4Ref);
                VerifyModelForOutFieldDuplicate(model, x4Decl[1], x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutFieldDuplicate(model, x5Decl, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutFieldDuplicate(model, x6Decl, x6Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);
                int[] exclude = new int[] { (int)ErrorCode.ERR_CompilationUnitUnexpected };

                compilation.GetDiagnostics().Where(d => !exclude.Contains(d.Code)).Verify(
                    // (4,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(4, 9),
                    // (13,52): error CS0128: A local variable or function named 'x4' is already defined in this scope
                    //                         H.TakeOutParam(42, out var x4));
                    Diagnostic(ErrorCode.ERR_LocalDuplicate, "x4").WithArguments("x4").WithLocation(13, 52),
                    // (21,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(21, 6),
                    // (23,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(23, 13),
                    // (23,25): error CS0103: The name 'x4' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x4").WithArguments("x4").WithLocation(23, 25),
                    // (23,29): error CS0103: The name 'x5' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x5").WithArguments("x5").WithLocation(23, 29),
                    // (23,33): error CS0103: The name 'x6' does not exist in the current context
                    //     H.Dummy(x1, x2, x3, x4, x5, x6);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x6").WithArguments("x6").WithLocation(23, 33)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                VerifyModelForOutVar(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);

                var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
                var x2Ref = GetReferences(tree, "x2").Single();
                VerifyModelForOutVar(model, x2Decl);
                VerifyNotAnOutLocal(model, x2Ref);

                var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
                var x3Ref = GetReferences(tree, "x3").Single();
                VerifyModelForOutVar(model, x3Decl);
                VerifyNotAnOutLocal(model, x3Ref);

                var x4Decl = GetOutVarDeclarations(tree, "x4").ToArray();
                var x4Ref = GetReferences(tree, "x4").Single();
                Assert.Equal(2, x4Decl.Length);
                VerifyModelForOutVar(model, x4Decl[0]);
                VerifyModelForOutVarDuplicateInSameScope(model, x4Decl[1]);
                VerifyNotInScope(model, x4Ref);

                var x5Decl = GetOutVarDeclarations(tree, "x5").Single();
                var x5Ref = GetReferences(tree, "x5").Single();
                VerifyModelForOutVar(model, x5Decl);
                VerifyNotInScope(model, x5Ref);

                var x6Decl = GetOutVarDeclarations(tree, "x6").Single();
                var x6Ref = GetReferences(tree, "x6").Single();
                VerifyModelForOutVar(model, x6Decl);
                VerifyNotInScope(model, x6Ref);
            }
        }

        [Fact]
        public void GlobalCode_EventDeclaration_03()
        {
            string source =
@"
System.Console.WriteLine(x1);
event System.Action d = H.TakeOutParam(1, out var x1);
Test();

void Test()
{
    System.Console.WriteLine(x1);
}

class H
{
    public static System.Action TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_EventDeclaration_04()
        {
            string source =
@"
static var a = InitA();
System.Console.WriteLine(x1);
static event System.Action b = H.TakeOutParam(1, out var x1);
Test();
static var c = InitB();

void Test()
{
    System.Console.WriteLine(x1);
}

static object InitA()
{
    System.Console.WriteLine(""InitA {0}"", x1);
    return null;
}

static object InitB()
{
    System.Console.WriteLine(""InitB {0}"", x1);
    return null;
}

class H
{
    public static System.Action TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"InitA 0
InitB 1
1
1").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(4, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_EventDeclaration_05()
        {
            string source =
@"
 
event System.Action b = H.TakeOutParam(1, out var x1);
static var d = x1;

static void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static System.Action TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.VerifyDiagnostics(
                // (4,16): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                // static var d = x1;
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(4, 16),
                // (8,13): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                //     H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(8, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_EventDeclaration_06()
        {
            string source =
@"
 
event System.Action b = H.TakeOutParam(1, out int x1);
static var d = x1;

static void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static System.Action TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.VerifyDiagnostics(
                // (4,16): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                // static var d = x1;
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(4, 16),
                // (8,13): error CS0120: An object reference is required for the non-static field, method, or property 'x1'
                //     H.Dummy(x1);
                Diagnostic(ErrorCode.ERR_ObjectRequired, "x1").WithArguments("x1").WithLocation(8, 13)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_EventDeclaration_07()
        {
            string source =
@"
Test();
event System.Action a = H.TakeOutParam(1, out var x1), b = Test(), c = H.TakeOutParam(2, out var x2);
Test();

System.Action Test()
{
    System.Console.WriteLine(""{0} {1}"", x1, x2);
    return null;
}

class H
{
    public static System.Action TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return null;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            CompileAndVerify(compilation, expectedOutput:
@"0 0
1 0
1 2").VerifyDiagnostics();

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutField(model, x2Decl, x2Ref);
        }

        [Fact]
        public void GlobalCode_DeclaratorArguments_01()
        {
            string source =
@"
 
bool a, b(out var x1);
H.Dummy(x1);

void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,10): error CS1528: Expected ; or = (cannot specify constructor arguments in declaration)
                // bool a, b(out var x1);
                Diagnostic(ErrorCode.ERR_BadVarDecl, "(out var x1").WithLocation(3, 10),
                // (3,10): error CS1003: Syntax error, '[' expected
                // bool a, b(out var x1);
                Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(3, 10),
                // (3,21): error CS1003: Syntax error, ']' expected
                // bool a, b(out var x1);
                Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(3, 21),
                // (3,19): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                // bool a, b(out var x1);
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(3, 19)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelForOutField(model, x1Decl, x1Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,10): error CS1528: Expected ; or = (cannot specify constructor arguments in declaration)
                    // bool a, b(out var x1);
                    Diagnostic(ErrorCode.ERR_BadVarDecl, "(out var x1").WithLocation(3, 10),
                    // (3,10): error CS1003: Syntax error, '[' expected
                    // bool a, b(out var x1);
                    Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(3, 10),
                    // (3,21): error CS1003: Syntax error, ']' expected
                    // bool a, b(out var x1);
                    Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(3, 21),
                    // (3,6): warning CS0168: The variable 'a' is declared but never used
                    // bool a, b(out var x1);
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "a").WithArguments("a").WithLocation(3, 6),
                    // (3,9): warning CS0168: The variable 'b' is declared but never used
                    // bool a, b(out var x1);
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "b").WithArguments("b").WithLocation(3, 9),
                    // (6,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(6, 6)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelForOutVarInNotExecutableCode(model, x1Decl, x1Ref);
            }
        }

        [Fact]
        public void GlobalCode_DeclaratorArguments_02()
        {
            string source =
@"
label: 
bool a, b(H.TakeOutParam(1, out var x1));
H.Dummy(x1);

void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,10): error CS1528: Expected ; or = (cannot specify constructor arguments in declaration)
                // bool a, b(H.TakeOutParam(1, out var x1));
                Diagnostic(ErrorCode.ERR_BadVarDecl, "(H.TakeOutParam(1, out var x1)").WithLocation(3, 10),
                // (3,10): error CS1003: Syntax error, '[' expected
                // bool a, b(H.TakeOutParam(1, out var x1));
                Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(3, 10),
                // (3,40): error CS1003: Syntax error, ']' expected
                // bool a, b(H.TakeOutParam(1, out var x1));
                Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(3, 40),
                // (2,1): warning CS0164: This label has not been referenced
                // label: 
                Diagnostic(ErrorCode.WRN_UnreferencedLabel, "label").WithLocation(2, 1)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelForOutField(model, x1Decl, x1Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,10): error CS1528: Expected ; or = (cannot specify constructor arguments in declaration)
                    // bool a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.ERR_BadVarDecl, "(H.TakeOutParam(1, out var x1)").WithLocation(3, 10),
                    // (3,10): error CS1003: Syntax error, '[' expected
                    // bool a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(3, 10),
                    // (3,40): error CS1003: Syntax error, ']' expected
                    // bool a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(3, 40),
                    // (2,1): warning CS0164: This label has not been referenced
                    // label: 
                    Diagnostic(ErrorCode.WRN_UnreferencedLabel, "label").WithLocation(2, 1),
                    // (4,9): error CS0165: Use of unassigned local variable 'x1'
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(4, 9),
                    // (3,6): warning CS0168: The variable 'a' is declared but never used
                    // bool a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "a").WithArguments("a").WithLocation(3, 6),
                    // (3,9): warning CS0168: The variable 'b' is declared but never used
                    // bool a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.WRN_UnreferencedVar, "b").WithArguments("b").WithLocation(3, 9),
                    // (6,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(6, 6)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelForOutVarInNotExecutableCode(model, x1Decl, x1Ref);
            }
        }

        [Fact]
        public void GlobalCode_DeclaratorArguments_03()
        {
            string source =
@"
 
event System.Action a, b(H.TakeOutParam(1, out var x1));
H.Dummy(x1);

void Test()
{
    H.Dummy(x1);
}

class H
{
    public static System.Action Dummy(params object[] x) {return null;}
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,25): error CS1528: Expected ; or = (cannot specify constructor arguments in declaration)
                // event System.Action a, b(H.TakeOutParam(1, out var x1));
                Diagnostic(ErrorCode.ERR_BadVarDecl, "(H.TakeOutParam(1, out var x1)").WithLocation(3, 25),
                // (3,25): error CS1003: Syntax error, '[' expected
                // event System.Action a, b(H.TakeOutParam(1, out var x1));
                Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(3, 25),
                // (3,55): error CS1003: Syntax error, ']' expected
                // event System.Action a, b(H.TakeOutParam(1, out var x1));
                Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(3, 55)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelForOutField(model, x1Decl, x1Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,25): error CS1528: Expected ; or = (cannot specify constructor arguments in declaration)
                    // event System.Action a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.ERR_BadVarDecl, "(H.TakeOutParam(1, out var x1)").WithLocation(3, 25),
                    // (3,25): error CS1003: Syntax error, '[' expected
                    // event System.Action a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.ERR_SyntaxError, "(").WithArguments("[").WithLocation(3, 25),
                    // (3,55): error CS1003: Syntax error, ']' expected
                    // event System.Action a, b(H.TakeOutParam(1, out var x1));
                    Diagnostic(ErrorCode.ERR_SyntaxError, ")").WithArguments("]").WithLocation(3, 55),
                    // (4,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(4, 9),
                    // (6,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(6, 6),
                    // (8,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(8, 13)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelNotSupported(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);
            }
        }

        [Fact]
        public void GlobalCode_DeclaratorArguments_04()
        {
            string source =
@"

fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
H.Dummy(x1);

void Test()
{
    H.Dummy(x1);
}

class H
{
    public static bool Dummy(params object[] x) {return true;}
    public static int TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return 3;
    }
}
";
            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"),
                                                                  parseOptions: TestOptions.Script);

                compilation.VerifyDiagnostics(
                // (3,18): error CS1642: Fixed size buffer fields may only be members of structs
                // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                Diagnostic(ErrorCode.ERR_FixedNotInStruct, "b").WithLocation(3, 18),
                // (3,20): error CS0133: The expression being assigned to 'b' must be constant
                // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "H.TakeOutParam(1, out var x1)").WithArguments("b").WithLocation(3, 20),
                // (3,12): error CS1642: Fixed size buffer fields may only be members of structs
                // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                Diagnostic(ErrorCode.ERR_FixedNotInStruct, "a").WithLocation(3, 12),
                // (3,12): error CS0214: Pointers and fixed size buffers may only be used in an unsafe context
                // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                Diagnostic(ErrorCode.ERR_UnsafeNeeded, "a[2]").WithLocation(3, 12)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelForOutField(model, x1Decl, x1Ref);
            }

            {
                var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular9);

                compilation.VerifyDiagnostics(
                    // (3,12): error CS9348: A compilation unit cannot directly contain members such as fields, methods or properties 
                    // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                    Diagnostic(ErrorCode.ERR_CompilationUnitUnexpected, "a").WithLocation(3, 12),
                    // (3,18): error CS1642: Fixed size buffer fields may only be members of structs
                    // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                    Diagnostic(ErrorCode.ERR_FixedNotInStruct, "b").WithLocation(3, 18),
                    // (3,20): error CS0133: The expression being assigned to '<invalid-global-code>.b' must be constant
                    // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                    Diagnostic(ErrorCode.ERR_NotConstantExpression, "H.TakeOutParam(1, out var x1)").WithArguments("<invalid-global-code>.b").WithLocation(3, 20),
                    // (3,12): error CS1642: Fixed size buffer fields may only be members of structs
                    // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                    Diagnostic(ErrorCode.ERR_FixedNotInStruct, "a").WithLocation(3, 12),
                    // (3,12): error CS0214: Pointers and fixed size buffers may only be used in an unsafe context
                    // fixed bool a[2], b[H.TakeOutParam(1, out var x1)];
                    Diagnostic(ErrorCode.ERR_UnsafeNeeded, "a[2]").WithLocation(3, 12),
                    // (4,9): error CS0103: The name 'x1' does not exist in the current context
                    // H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(4, 9),
                    // (8,13): error CS0103: The name 'x1' does not exist in the current context
                    //     H.Dummy(x1);
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "x1").WithArguments("x1").WithLocation(8, 13),
                    // (6,6): warning CS8321: The local function 'Test' is declared but never used
                    // void Test()
                    Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Test").WithArguments("Test").WithLocation(6, 6)
                    );

                var tree = compilation.SyntaxTrees.Single();
                var model = compilation.GetSemanticModel(tree);

                var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
                var x1Ref = GetReferences(tree, "x1").ToArray();
                Assert.Equal(2, x1Ref.Length);
                AssertContainedInDeclaratorArguments(x1Decl);
                VerifyModelNotSupported(model, x1Decl);
                VerifyNotInScope(model, x1Ref[0]);
                VerifyNotInScope(model, x1Ref[1]);
            }
        }

        [Fact]
        public void GlobalCode_RestrictedType_01()
        {
            string source =
@"
 
H.TakeOutParam(out var x1);

H.TakeOutParam(out System.ArgIterator x2);

class H
{
    public static void TakeOutParam(out System.ArgIterator x) 
    {
        x = default(System.ArgIterator);
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.GetDeclarationDiagnostics().Verify(
                // (9,37): error CS1601: Cannot make reference to variable of type 'ArgIterator'
                //     public static void TakeOutParam(out System.ArgIterator x) 
                Diagnostic(ErrorCode.ERR_MethodArgCantBeRefAny, "out System.ArgIterator x").WithArguments("System.ArgIterator").WithLocation(9, 37),
                // (5,20): error CS0610: Field or property cannot be of type 'ArgIterator'
                // H.TakeOutParam(out System.ArgIterator x2);
                Diagnostic(ErrorCode.ERR_FieldCantBeRefAny, "System.ArgIterator").WithArguments("System.ArgIterator").WithLocation(5, 20),
                // (3,20): error CS0610: Field or property cannot be of type 'ArgIterator'
                // H.TakeOutParam(out var x1);
                Diagnostic(ErrorCode.ERR_FieldCantBeRefAny, "var").WithArguments("System.ArgIterator").WithLocation(3, 20)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            VerifyModelForOutField(model, x2Decl);
        }

        [Fact]
        public void GlobalCode_StaticType_01()
        {
            string source =
@"
 
H.TakeOutParam(out var x1);

H.TakeOutParam(out StaticType x2);

class H
{
    public static void TakeOutParam(out StaticType x) 
    {
        x = default(System.ArgIterator);
    }
}

static class StaticType{}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.GetDeclarationDiagnostics().Verify(
                // (5,31): error CS0723: Cannot declare a variable of static type 'StaticType'
                // H.TakeOutParam(out StaticType x2);
                Diagnostic(ErrorCode.ERR_VarDeclIsStaticClass, "x2").WithArguments("StaticType").WithLocation(5, 31),
                // (9,41): error CS0721: 'StaticType': static types cannot be used as parameters
                //     public static void TakeOutParam(out StaticType x) 
                Diagnostic(ErrorCode.ERR_ParameterIsStaticClass, "StaticType").WithArguments("StaticType").WithLocation(9, 41),
                // (3,24): error CS0723: Cannot declare a variable of static type 'StaticType'
                // H.TakeOutParam(out var x1);
                Diagnostic(ErrorCode.ERR_VarDeclIsStaticClass, "x1").WithArguments("StaticType").WithLocation(3, 24)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            VerifyModelForOutField(model, x2Decl);
        }

        [Fact]
        public void GlobalCode_InferenceFailure_01()
        {
            string source =
@"
 
H.TakeOutParam(out var x1, x1);

class H
{
    public static void TakeOutParam(out int x, long y) 
    {
        x = 1;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.GetDeclarationDiagnostics().Verify(
                // (3,24): error CS7019: Type of 'x1' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // H.TakeOutParam(out var x1, x1);
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "x1").WithArguments("x1").WithLocation(3, 24)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
            var x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("var", x1.Type.ToTestDisplayString());
            Assert.True(x1.Type.IsErrorType());
        }

        [Fact]
        public void GlobalCode_InferenceFailure_02()
        {
            string source =
@"
 
var a = b;
var b = H.TakeOutParam(out var x1, a);

class H
{
    public static int TakeOutParam(out int x, long y) 
    {
        x = 1;
        return 123;
    }
}
";
            // `skipUsesIsNullable: true` is necessary to avoid visiting symbols eagerly in CreateCompilation,
            // which would result in `ERR_RecursivelyTypedVariable` reported on the other local (field).
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script, skipUsesIsNullable: true);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var b = (IFieldSymbol)model.GetDeclaredSymbol(tree.GetRoot().DescendantNodes().OfType<VariableDeclaratorSyntax>().Where(d => d.Identifier.ValueText == "b").Single());
            Assert.True(b.Type.IsErrorType());

            compilation.VerifyDiagnostics(
                // (4,5): error CS7019: Type of 'b' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // var b = H.TakeOutParam(out var x1, a);
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "b").WithArguments("b").WithLocation(4, 5)
                );

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl);
            var x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("System.Int32", x1.Type.ToTestDisplayString());
        }

        [Fact]
        public void GlobalCode_InferenceFailure_03()
        {
            string source =
@"
 
var a = H.TakeOutParam(out var x1, b);
var b = a;

class H
{
    public static int TakeOutParam(out int x, long y) 
    {
        x = 1;
        return 123;
    }
}
";
            // `skipUsesIsNullable: true` is necessary to avoid visiting symbols eagerly in CreateCompilation,
            // which would result in `ERR_RecursivelyTypedVariable` reported on the other local (field).
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script, skipUsesIsNullable: true);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var b = (IFieldSymbol)model.GetDeclaredSymbol(tree.GetRoot().DescendantNodes().OfType<VariableDeclaratorSyntax>().Where(d => d.Identifier.ValueText == "b").Single());
            Assert.True(b.Type.IsErrorType());

            compilation.VerifyDiagnostics(
                // (4,5): error CS7019: Type of 'b' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // var b = a;
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "b").WithArguments("b").WithLocation(4, 5)
                );

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl);
            var x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("System.Int32", x1.Type.ToTestDisplayString());
        }

        [Fact]
        public void GlobalCode_InferenceFailure_04()
        {
            string source =
@"
 
var a = x1;
var b = H.TakeOutParam(out var x1, a);

class H
{
    public static int TakeOutParam(out int x, long y) 
    {
        x = 1;
        return 123;
    }
}
";
            // `skipUsesIsNullable: true` is necessary to avoid visiting symbols eagerly in CreateCompilation,
            // which would result in `ERR_RecursivelyTypedVariable` reported on the other local (field).
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script, skipUsesIsNullable: true);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var a = (IFieldSymbol)model.GetDeclaredSymbol(tree.GetRoot().DescendantNodes().OfType<VariableDeclaratorSyntax>().Where(d => d.Identifier.ValueText == "a").Single());
            Assert.True(a.Type.IsErrorType());

            compilation.VerifyDiagnostics(
                // (3,5): error CS7019: Type of 'a' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // var a = x1;
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "a").WithArguments("a").WithLocation(3, 5)
                );

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl);
            var x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("System.Int32", x1.Type.ToTestDisplayString());

            compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script, skipUsesIsNullable: true);
            tree = compilation.SyntaxTrees.Single();
            model = compilation.GetSemanticModel(tree);
            x1Decl = GetOutVarDeclarations(tree, "x1").Single();

            x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("var", x1.Type.ToTestDisplayString());
            Assert.True(x1.Type.IsErrorType());

            compilation.VerifyDiagnostics(
                // (4,32): error CS7019: Type of 'x1' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // var b = H.TakeOutParam(out var x1, a);
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "x1").WithArguments("x1").WithLocation(4, 32)
                );
        }

        [Fact]
        public void GlobalCode_InferenceFailure_05()
        {
            string source =
@"
 
var a = H.TakeOutParam(out var x1, b);
var b = x1;

class H
{
    public static int TakeOutParam(out int x, long y) 
    {
        x = 1;
        return 123;
    }
}
";
            // `skipUsesIsNullable: true` is necessary to avoid visiting symbols eagerly in CreateCompilation,
            // which would result in `ERR_RecursivelyTypedVariable` reported on the other local (field).
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script, skipUsesIsNullable: true);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl);
            var x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("var", x1.Type.ToTestDisplayString());
            Assert.True(x1.Type.IsErrorType());

            compilation.VerifyDiagnostics(
                // (3,32): error CS7019: Type of 'x1' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // var a = H.TakeOutParam(out var x1, b);
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "x1").WithArguments("x1").WithLocation(3, 32)
                );

            compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script, skipUsesIsNullable: true);
            tree = compilation.SyntaxTrees.Single();
            model = compilation.GetSemanticModel(tree);

            x1Decl = GetOutVarDeclarations(tree, "x1").Single();

            var bDecl = tree.GetRoot().DescendantNodes().OfType<VariableDeclaratorSyntax>().Where(d => d.Identifier.ValueText == "b").Single();
            var b = (IFieldSymbol)model.GetDeclaredSymbol(bDecl);
            Assert.True(b.Type.IsErrorType());

            x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("System.Int32", x1.Type.ToTestDisplayString());
            Assert.False(x1.Type.IsErrorType());

            compilation.VerifyDiagnostics(
                // (4,5): error CS7019: Type of 'b' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // var b = x1;
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "b").WithArguments("b").WithLocation(4, 5)
                );
        }

        [Fact]
        public void GlobalCode_InferenceFailure_06()
        {
            string source =
@"
H.TakeOutParam(out var x1);

class H
{
    public static int TakeOutParam<T>(out T x) 
    {
        x = default(T);
        return 123;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            compilation.VerifyDiagnostics(
                // (2,24): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                // H.TakeOutParam(out var x1);
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(2, 24),
                // (2,3): error CS0411: The type arguments for method 'H.TakeOutParam<T>(out T)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
                // H.TakeOutParam(out var x1);
                Diagnostic(ErrorCode.ERR_CantInferMethTypeArgs, "TakeOutParam").WithArguments("H.TakeOutParam<T>(out T)").WithLocation(2, 3)
                );

            compilation.GetDeclarationDiagnostics().Verify(
                // (2,24): error CS8197: Cannot infer the type of implicitly-typed out variable 'x1'.
                // H.TakeOutParam(out var x1);
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "x1").WithArguments("x1").WithLocation(2, 24)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            VerifyModelForOutField(model, x1Decl);
            var x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("var", x1.Type.ToTestDisplayString());
            Assert.True(x1.Type.IsErrorType());
        }

        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/17377")]
        public void GlobalCode_InferenceFailure_07()
        {
            string source =
@"
H.M((var x1, int x2));
H.M(x1);

class H
{
    public static void M(object a) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);
            compilation.VerifyDiagnostics(
                // (2,10): error CS7019: Type of 'x1' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // H.M((var x1, int x2));
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "x1").WithArguments("x1").WithLocation(2, 10),
                // (2,6): error CS8185: A declaration is not allowed in this context.
                // H.M((var x1, int x2));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "var x1").WithLocation(2, 6),
                // (2,14): error CS8185: A declaration is not allowed in this context.
                // H.M((var x1, int x2));
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "int x2").WithLocation(2, 14),
                // (2,5): error CS8179: Predefined type 'System.ValueTuple`2' is not defined or imported
                // H.M((var x1, int x2));
                Diagnostic(ErrorCode.ERR_PredefinedValueTupleTypeNotFound, "(var x1, int x2)").WithArguments("System.ValueTuple`2").WithLocation(2, 5),
                // (2,5): error CS1503: Argument 1: cannot convert from '(var, int)' to 'object'
                // H.M((var x1, int x2));
                Diagnostic(ErrorCode.ERR_BadArgType, "(var x1, int x2)").WithArguments("1", "(var, int)", "object").WithLocation(2, 5)
                );
            compilation.GetDeclarationDiagnostics().Verify(
                // (2,10): error CS7019: Type of 'x1' cannot be inferred since its initializer directly or indirectly refers to the definition.
                // H.M((var x1, int x2));
                Diagnostic(ErrorCode.ERR_RecursivelyTypedVariable, "x1").WithArguments("x1").WithLocation(2, 10)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = tree.GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>()
                    .Where(p => p.Identifier().ValueText == "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(1, x1Ref.Length);
            VerifyModelForOutField(model, x1Decl, x1Ref);
            var x1 = (IFieldSymbol)model.GetDeclaredSymbol(x1Decl.VariableDesignation());
            Assert.Equal("var", x1.Type.ToTestDisplayString());
            Assert.True(x1.Type.IsErrorType());
        }

        [Fact, WorkItem(17321, "https://github.com/dotnet/roslyn/issues/17321")]
        public void InferenceFailure_01()
        {
            string source =
@"
class H
{
    object M1() => M(M(1), x1);
    static object M(object o1) => o1;
    static void M(object o1, object o2) {}
}
";
            var node0 = SyntaxFactory.ParseCompilationUnit(source);
            var one = node0.DescendantNodes().OfType<LiteralExpressionSyntax>().Single();
            var decl = SyntaxFactory.DeclarationExpression(
                type: SyntaxFactory.IdentifierName(SyntaxFactory.Identifier("var")),
                designation: SyntaxFactory.SingleVariableDesignation(SyntaxFactory.Identifier("x1")));
            var node1 = node0.ReplaceNode(one, decl);
            var tree = node1.SyntaxTree;
            Assert.NotNull(tree);
            var compilation = CreateCompilation(new[] { tree });
            compilation.VerifyDiagnostics(
                // (4,24): error CS8185: A declaration is not allowed in this context.
                //     object M1() => M(M(varx1), x1);
                Diagnostic(ErrorCode.ERR_DeclarationExpressionNotPermitted, "varx1").WithLocation(4, 24)
                );

            var model = compilation.GetSemanticModel(tree);
            var x1Decl = tree.GetRoot().DescendantNodes().OfType<DeclarationExpressionSyntax>()
                    .Where(p => p.Identifier().ValueText == "x1").Single();
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForDeclarationVarWithoutDataFlow(model, x1Decl, x1Ref);
        }

        [Fact]
        public void GlobalCode_AliasInfo_01()
        {
            string source =
@"
H.TakeOutParam(1, out var x1);

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            Assert.Null(model.GetAliasInfo(x1Decl.Type));
        }

        [Fact]
        public void GlobalCode_AliasInfo_02()
        {
            string source =
@"
using var = System.Int32;

H.TakeOutParam(1, out var x1);

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            Assert.Equal("var=System.Int32", model.GetAliasInfo(x1Decl.Type).ToTestDisplayString());
        }

        [Fact]
        public void GlobalCode_AliasInfo_03()
        {
            string source =
@"
using a = System.Int32;

H.TakeOutParam(1, out a x1);

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            Assert.Equal("a=System.Int32", model.GetAliasInfo(x1Decl.Type).ToTestDisplayString());
        }

        [Fact]
        public void GlobalCode_AliasInfo_04()
        {
            string source =
@"
H.TakeOutParam(1, out int x1);

class H
{
    public static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.ReleaseExe.WithScriptClassName("Script"), parseOptions: TestOptions.Script);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            Assert.Null(model.GetAliasInfo(x1Decl.Type));
        }

        [Fact, WorkItem(14717, "https://github.com/dotnet/roslyn/issues/14717")]
        public void ExpressionVariableInCase_1()
        {
            string source =
@"
class Program
{
    static void Main(string[] args)
    {
        switch (true)
        {
            case !TakeOutParam(3, out var x1):
                System.Console.WriteLine(x1);
                break;
        }
    }
    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            // The point of this test is that it should not crash.
            compilation.VerifyDiagnostics(
                // (8,18): error CS9135: A constant value of type 'bool' is expected
                //             case !TakeOutParam(3, out var x1):
                Diagnostic(ErrorCode.ERR_ConstantValueOfTypeExpected, "!TakeOutParam(3, out var x1)").WithArguments("bool").WithLocation(8, 18)
            );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVarInNotExecutableCode(model, x1Decl, x1Ref);
        }

        [Fact, WorkItem(14717, "https://github.com/dotnet/roslyn/issues/14717")]
        public void ExpressionVariableInCase_2()
        {
            string source =
@"
class Program
{
    static void Main(string[] args)
    {
        switch (true)
        {
            case !TakeOutParam(3, out UndeclaredType x1):
                System.Console.WriteLine(x1);
                break;
        }
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            // The point of this test is that it should not crash.
            compilation.VerifyDiagnostics(
                // (8,19): error CS0103: The name 'TakeOutParam' does not exist in the current context
                //             case !TakeOutParam(3, out UndeclaredType x1):
                Diagnostic(ErrorCode.ERR_NameNotInContext, "TakeOutParam").WithArguments("TakeOutParam").WithLocation(8, 19),
                // (8,39): error CS0246: The type or namespace name 'UndeclaredType' could not be found (are you missing a using directive or an assembly reference?)
                //             case !TakeOutParam(3, out UndeclaredType x1):
                Diagnostic(ErrorCode.ERR_SingleTypeNameNotFound, "UndeclaredType").WithArguments("UndeclaredType").WithLocation(8, 39)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);
            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVarInNotExecutableCode(model, x1Decl, x1Ref);
        }

        private static void VerifyModelForOutField(
            SemanticModel model,
            DeclarationExpressionSyntax decl,
            params IdentifierNameSyntax[] references)
        {
            VerifyModelForOutField(model, decl, false, references);
        }

        private static void VerifyModelForOutFieldDuplicate(
            SemanticModel model,
            DeclarationExpressionSyntax decl,
            params IdentifierNameSyntax[] references)
        {
            VerifyModelForOutField(model, decl, true, references);
        }

        private static void VerifyModelForOutField(
            SemanticModel model,
            DeclarationExpressionSyntax decl,
            bool duplicate,
            params IdentifierNameSyntax[] references)
        {
            var variableDesignationSyntax = GetVariableDesignation(decl);
            var symbol = model.GetDeclaredSymbol(variableDesignationSyntax);
            Assert.Equal(decl.Identifier().ValueText, symbol.Name);
            Assert.Equal(SymbolKind.Field, symbol.Kind);
            Assert.Equal(variableDesignationSyntax, symbol.DeclaringSyntaxReferences.Single().GetSyntax());
            Assert.Same(symbol, model.GetDeclaredSymbol((SyntaxNode)variableDesignationSyntax));

            var symbols = model.LookupSymbols(decl.SpanStart, name: decl.Identifier().ValueText);
            var names = model.LookupNames(decl.SpanStart);

            if (duplicate)
            {
                Assert.True(symbols.Count() > 1);
                Assert.Contains(symbol, symbols);
            }
            else
            {
                Assert.Same(symbol, symbols.Single());
            }

            Assert.Contains(decl.Identifier().ValueText, names);

            var local = (IFieldSymbol)symbol;

            var declarator = decl.Ancestors().OfType<VariableDeclaratorSyntax>().FirstOrDefault();
            var inFieldDeclaratorArgumentlist = declarator != null && declarator.Parent.Parent.Kind() != SyntaxKind.LocalDeclarationStatement &&
                                           (declarator.ArgumentList?.Contains(decl)).GetValueOrDefault();

            // We're not able to get type information at such location (out var argument in global code) at this point
            // See https://github.com/dotnet/roslyn/issues/13569
            AssertInfoForDeclarationExpressionSyntax(model, decl, expectedSymbol: local, expectedType: inFieldDeclaratorArgumentlist ? null : local.Type);

            foreach (var reference in references)
            {
                var referenceInfo = model.GetSymbolInfo(reference);
                symbols = model.LookupSymbols(reference.SpanStart, name: decl.Identifier().ValueText);

                if (duplicate)
                {
                    Assert.Null(referenceInfo.Symbol);
                    Assert.Contains(symbol, referenceInfo.CandidateSymbols);
                    Assert.True(symbols.Count() > 1);
                    Assert.Contains(symbol, symbols);
                }
                else
                {
                    Assert.Same(symbol, referenceInfo.Symbol);
                    Assert.Same(symbol, symbols.Single());
                    Assert.Equal(local.Type, model.GetTypeInfo(reference).Type);
                }

                Assert.True(model.LookupNames(reference.SpanStart).Contains(decl.Identifier().ValueText));
            }

            if (!inFieldDeclaratorArgumentlist)
            {
                var dataFlowParent = (ExpressionSyntax)decl.Parent.Parent.Parent;

                if (model.IsSpeculativeSemanticModel)
                {
                    Assert.Throws<NotSupportedException>(() => model.AnalyzeDataFlow(dataFlowParent));
                }
                else
                {
                    var dataFlow = model.AnalyzeDataFlow(dataFlowParent);

                    if (dataFlow.Succeeded)
                    {
                        Assert.False(dataFlow.VariablesDeclared.Contains(symbol, ReferenceEqualityComparer.Instance));
                        Assert.False(dataFlow.AlwaysAssigned.Contains(symbol, ReferenceEqualityComparer.Instance));
                        Assert.False(dataFlow.WrittenInside.Contains(symbol, ReferenceEqualityComparer.Instance));
                        Assert.False(dataFlow.DataFlowsIn.Contains(symbol, ReferenceEqualityComparer.Instance));
                        Assert.False(dataFlow.ReadInside.Contains(symbol, ReferenceEqualityComparer.Instance));
                        Assert.False(dataFlow.DataFlowsOut.Contains(symbol, ReferenceEqualityComparer.Instance));
                        Assert.False(dataFlow.ReadOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
                        Assert.False(dataFlow.WrittenOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
                    }
                }
            }
        }

        [Fact]
        public void MethodTypeArgumentInference_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        TakeOutParam(out int a);
        TakeOutParam(out long b);
    }

    static void TakeOutParam<T>(out T x) 
    {
        x = default(T);
        System.Console.WriteLine(typeof(T));
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"System.Int32
System.Int64");
        }

        [Fact]
        public void MethodTypeArgumentInference_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        TakeOutParam(out var a);
    }

    static void TakeOutParam<T>(out T x) 
    {
        x = default(T);
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (6,9): error CS0411: The type arguments for method 'X.TakeOutParam<T>(out T)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
                //         TakeOutParam(out var a);
                Diagnostic(ErrorCode.ERR_CantInferMethTypeArgs, "TakeOutParam").WithArguments("X.TakeOutParam<T>(out T)").WithLocation(6, 9)
                );
        }

        [Fact]
        public void MethodTypeArgumentInference_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        long a = 0;
        TakeOutParam(out int b, a);
        int c;
        TakeOutParam(out c, a);
    }

    static void TakeOutParam<T>(out T x, T y) 
    {
        x = default(T);
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics(
                // (7,9): error CS0411: The type arguments for method 'X.TakeOutParam<T>(out T, T)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
                //         TakeOutParam(out int b, a);
                Diagnostic(ErrorCode.ERR_CantInferMethTypeArgs, "TakeOutParam").WithArguments("X.TakeOutParam<T>(out T, T)").WithLocation(7, 9),
                // (9,9): error CS0411: The type arguments for method 'X.TakeOutParam<T>(out T, T)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
                //         TakeOutParam(out c, a);
                Diagnostic(ErrorCode.ERR_CantInferMethTypeArgs, "TakeOutParam").WithArguments("X.TakeOutParam<T>(out T, T)").WithLocation(9, 9)
                );
        }

        [Fact]
        public void MethodTypeArgumentInference_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        byte a = 0;
        int b = 0;
        TakeOutParam(out int c, a);
        TakeOutParam(out b, a);
    }

    static void TakeOutParam<T>(out T x, T y) 
    {
        x = default(T);
        System.Console.WriteLine(typeof(T));
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput:
@"System.Int32
System.Int32");
        }

        [Fact, WorkItem(14825, "https://github.com/dotnet/roslyn/issues/14825")]
        public void OutVarDeclaredInReceiverUsedInArgument()
        {
            var source =
@"using System.Linq;

public class C
{
    public string[] Goo2(out string x) { x = """"; return null; }
    public string[] Goo3(bool b) { return null; }

    public string[] Goo5(string u) { return null; }
    
    public void Test()
    {
        var t1 = Goo2(out var x1).Concat(Goo5(x1));
        var t2 = Goo3(t1 is var x2).Concat(Goo5(x2.First()));
    }
}
";
            var compilation = CreateCompilationWithMscorlib40AndSystemCore(source, options: TestOptions.DebugDll, parseOptions: TestOptions.Regular);
            compilation.VerifyDiagnostics();
            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVar(model, x1Decl, x1Ref);
            Assert.Equal("System.String", model.GetTypeInfo(x1Ref).Type.ToTestDisplayString());
        }

        [Fact]
        public void OutVarDiscard()
        {
            var source =
@"
public class C
{
    static void Main()
    {
        M(out int _);
        M(out var _);
        M(out _);
    }

    static void M(out int x) { x = 1; System.Console.Write(""M""); }
}
";
            var comp = CompileAndVerify(source, expectedOutput: "MMM");
            comp.VerifyDiagnostics();

            var tree = comp.Compilation.SyntaxTrees.Single();
            var model = comp.Compilation.GetSemanticModel(tree);

            var discard1 = GetDiscardDesignations(tree).ElementAt(0);
            Assert.Null(model.GetDeclaredSymbol(discard1));
            Assert.Null(model.GetTypeInfo(discard1).Type);
            Assert.Null(model.GetSymbolInfo(discard1).Symbol);
            var declaration1 = (DeclarationExpressionSyntax)discard1.Parent;
            Assert.Equal("int _", declaration1.ToString());
            Assert.Equal("System.Int32", model.GetTypeInfo(declaration1).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration1).Symbol);

            var discard2 = GetDiscardDesignations(tree).ElementAt(1);
            Assert.Null(model.GetDeclaredSymbol(discard2));
            Assert.Null(model.GetTypeInfo(discard2).Type);
            Assert.Null(model.GetSymbolInfo(discard2).Symbol);
            var declaration2 = (DeclarationExpressionSyntax)discard2.Parent;
            Assert.Equal("var _", declaration2.ToString());
            Assert.Equal("System.Int32", model.GetTypeInfo(declaration2).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration2).Symbol);

            var discard3 = GetDiscardIdentifiers(tree).First();
            Assert.Null(model.GetDeclaredSymbol(discard3));
            var discard3Symbol = (IDiscardSymbol)model.GetSymbolInfo(discard3).Symbol;
            Assert.Equal("System.Int32", discard3Symbol.Type.ToTestDisplayString());
            Assert.Equal("System.Int32", model.GetTypeInfo(discard3).Type.ToTestDisplayString());

            comp.VerifyIL("C.Main()", @"
{
  // Code size       22 (0x16)
  .maxstack  1
  .locals init (int V_0)
  IL_0000:  ldloca.s   V_0
  IL_0002:  call       ""void C.M(out int)""
  IL_0007:  ldloca.s   V_0
  IL_0009:  call       ""void C.M(out int)""
  IL_000e:  ldloca.s   V_0
  IL_0010:  call       ""void C.M(out int)""
  IL_0015:  ret
}
");
        }

        [Fact]
        public void NamedOutVarDiscard()
        {
            var source =
@"
public class C
{
    static void Main()
    {
        M(y: out string _, x: out int _);
        M(y: out var _, x: out var _);
        M(y: out _, x: out _);
    }

    static void M(out int x, out string y) { x = 1; y = ""hello""; System.Console.Write(""M""); }
}
";
            var comp = CompileAndVerify(source, expectedOutput: "MMM");
            comp.VerifyDiagnostics();
        }

        [Fact]
        public void OutVarDiscardInCtor_01()
        {
            var source =
    @"
public class C
{
    public C(out int i) { i = 1; System.Console.Write(""C""); }
    static void Main()
    {
        new C(out int i1);
        new C(out int _);
        new C(out var _);
        new C(out _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics();
            CompileAndVerify(comp, expectedOutput: "CCCC");

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var discard1 = GetDiscardDesignations(tree).ElementAt(0);
            Assert.Null(model.GetDeclaredSymbol(discard1));
            Assert.Null(model.GetSymbolInfo(discard1).Symbol);
            var declaration1 = (DeclarationExpressionSyntax)discard1.Parent;
            Assert.Equal("int _", declaration1.ToString());
            Assert.Equal("System.Int32", model.GetTypeInfo(declaration1).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration1).Symbol);

            Assert.Equal("int", declaration1.Type.ToString());
            Assert.Equal("System.Int32", model.GetSymbolInfo(declaration1.Type).Symbol.ToTestDisplayString());
            TypeInfo typeInfo = model.GetTypeInfo(declaration1.Type);
            Assert.Equal("System.Int32", typeInfo.Type.ToTestDisplayString());
            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
            Assert.True(model.GetConversion(declaration1.Type).IsIdentity);
            Assert.Null(model.GetAliasInfo(declaration1.Type));

            var discard2 = GetDiscardDesignations(tree).ElementAt(1);
            Assert.Null(model.GetDeclaredSymbol(discard2));
            Assert.Null(model.GetSymbolInfo(discard2).Symbol);
            var declaration2 = (DeclarationExpressionSyntax)discard2.Parent;
            Assert.Equal("var _", declaration2.ToString());
            Assert.Equal("System.Int32", model.GetTypeInfo(declaration2).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration2).Symbol);

            Assert.Equal("var", declaration2.Type.ToString());
            Assert.Equal("System.Int32", model.GetSymbolInfo(declaration2.Type).Symbol.ToTestDisplayString());
            typeInfo = model.GetTypeInfo(declaration2.Type);
            Assert.Equal("System.Int32", typeInfo.Type.ToTestDisplayString());
            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
            Assert.True(model.GetConversion(declaration2.Type).IsIdentity);
            Assert.Null(model.GetAliasInfo(declaration2.Type));

            var discard3 = GetDiscardIdentifiers(tree).First();
            Assert.Equal("System.Int32", model.GetTypeInfo(discard3).Type.ToTestDisplayString());
            var discard3Symbol = (IDiscardSymbol)model.GetSymbolInfo(discard3).Symbol;
            Assert.Equal("int _", discard3Symbol.ToDisplayString(SymbolDisplayFormat.MinimallyQualifiedFormat));
        }

        [Fact]
        public void OutVarDiscardInCtor_02()
        {
            var source =
    @"
public class C
{
    public C(out int i) { i = 1; System.Console.Write(""C""); }
    static void Main()
    {
        new C(out long x1);
        new C(out long _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics(
                // (7,19): error CS1503: Argument 1: cannot convert from 'out long' to 'out int'
                //         new C(out long x1);
                Diagnostic(ErrorCode.ERR_BadArgType, "long x1").WithArguments("1", "out long", "out int").WithLocation(7, 19),
                // (8,19): error CS1503: Argument 1: cannot convert from 'out long' to 'out int'
                //         new C(out long _);
                Diagnostic(ErrorCode.ERR_BadArgType, "long _").WithArguments("1", "out long", "out int").WithLocation(8, 19),
                // (7,19): error CS0165: Use of unassigned local variable 'x1'
                //         new C(out long x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "long x1").WithArguments("x1").WithLocation(7, 19)
                );

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl);

            var discard1 = GetDiscardDesignations(tree).Single();
            Assert.Null(model.GetDeclaredSymbol(discard1));
            Assert.Null(model.GetSymbolInfo(discard1).Symbol);
            var declaration1 = (DeclarationExpressionSyntax)discard1.Parent;
            Assert.Equal("long _", declaration1.ToString());
            Assert.Equal("System.Int64", model.GetTypeInfo(declaration1).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration1).Symbol);

            Assert.Equal("long", declaration1.Type.ToString());
            Assert.Equal("System.Int64", model.GetSymbolInfo(declaration1.Type).Symbol.ToTestDisplayString());
            TypeInfo typeInfo = model.GetTypeInfo(declaration1.Type);
            Assert.Equal("System.Int64", typeInfo.Type.ToTestDisplayString());
            Assert.Equal("System.Int64", typeInfo.ConvertedType.ToTestDisplayString());
            Assert.True(model.GetConversion(declaration1.Type).IsIdentity);
            Assert.Null(model.GetAliasInfo(declaration1.Type));
        }

        [Fact]
        public void OutVarDiscardAliasInfo_01()
        {
            var source =
@"
using alias1 = System.Int32;
using @var = System.Int32;

public class C
{
    public C(out int i) { i = 1; System.Console.Write(""C""); }
    static void Main()
    {
        new C(out alias1 _);
        new C(out var _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics();
            CompileAndVerify(comp, expectedOutput: "CC");

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var discard1 = GetDiscardDesignations(tree).ElementAt(0);
            Assert.Null(model.GetDeclaredSymbol(discard1));
            Assert.Null(model.GetSymbolInfo(discard1).Symbol);
            var declaration1 = (DeclarationExpressionSyntax)discard1.Parent;
            Assert.Equal("alias1 _", declaration1.ToString());
            Assert.Equal("System.Int32", model.GetTypeInfo(declaration1).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration1).Symbol);

            Assert.Equal("alias1", declaration1.Type.ToString());
            Assert.Equal("System.Int32", model.GetSymbolInfo(declaration1.Type).Symbol.ToTestDisplayString());
            TypeInfo typeInfo = model.GetTypeInfo(declaration1.Type);
            Assert.Equal("System.Int32", typeInfo.Type.ToTestDisplayString());
            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
            Assert.True(model.GetConversion(declaration1.Type).IsIdentity);
            Assert.Equal("alias1=System.Int32", model.GetAliasInfo(declaration1.Type).ToTestDisplayString());

            var discard2 = GetDiscardDesignations(tree).ElementAt(1);
            Assert.Null(model.GetDeclaredSymbol(discard2));
            Assert.Null(model.GetSymbolInfo(discard2).Symbol);
            var declaration2 = (DeclarationExpressionSyntax)discard2.Parent;
            Assert.Equal("var _", declaration2.ToString());
            Assert.Equal("System.Int32", model.GetTypeInfo(declaration2).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration2).Symbol);

            Assert.Equal("var", declaration2.Type.ToString());
            Assert.Equal("System.Int32", model.GetSymbolInfo(declaration2.Type).Symbol.ToTestDisplayString());
            typeInfo = model.GetTypeInfo(declaration2.Type);
            Assert.Equal("System.Int32", typeInfo.Type.ToTestDisplayString());
            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
            Assert.True(model.GetConversion(declaration2.Type).IsIdentity);
            Assert.Equal("var=System.Int32", model.GetAliasInfo(declaration2.Type).ToTestDisplayString());
        }

        [Fact]
        public void OutVarDiscardAliasInfo_02()
        {
            var source =
@"
enum alias1 : long {}
class @var {}

public class C
{
    public C(out int i) { i = 1; System.Console.Write(""C""); }
    static void Main()
    {
        new C(out alias1 _);
        new C(out var _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics(
                // (10,19): error CS1503: Argument 1: cannot convert from 'out alias1' to 'out int'
                //         new C(out alias1 _);
                Diagnostic(ErrorCode.ERR_BadArgType, "alias1 _").WithArguments("1", "out alias1", "out int").WithLocation(10, 19),
                // (11,19): error CS1503: Argument 1: cannot convert from 'out var' to 'out int'
                //         new C(out var _);
                Diagnostic(ErrorCode.ERR_BadArgType, "var _").WithArguments("1", "out var", "out int").WithLocation(11, 19)
                );

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var discard1 = GetDiscardDesignations(tree).ElementAt(0);
            Assert.Null(model.GetDeclaredSymbol(discard1));
            Assert.Null(model.GetSymbolInfo(discard1).Symbol);
            var declaration1 = (DeclarationExpressionSyntax)discard1.Parent;
            Assert.Equal("alias1 _", declaration1.ToString());
            Assert.Equal("alias1", model.GetTypeInfo(declaration1).Type.ToTestDisplayString());
            Assert.Null(model.GetSymbolInfo(declaration1).Symbol);

            Assert.Equal("alias1", declaration1.Type.ToString());
            Assert.Equal("alias1", model.GetSymbolInfo(declaration1.Type).Symbol.ToTestDisplayString());
            TypeInfo typeInfo = model.GetTypeInfo(declaration1.Type);
            Assert.Equal("alias1", typeInfo.Type.ToTestDisplayString());
            Assert.Equal("alias1", typeInfo.ConvertedType.ToTestDisplayString());
            Assert.True(model.GetConversion(declaration1.Type).IsIdentity);
            Assert.Null(model.GetAliasInfo(declaration1.Type));

            var discard2 = GetDiscardDesignations(tree).ElementAt(1);
            Assert.Null(model.GetDeclaredSymbol(discard2));
            Assert.Null(model.GetSymbolInfo(discard2).Symbol);
            var declaration2 = (DeclarationExpressionSyntax)discard2.Parent;
            Assert.Equal("var _", declaration2.ToString());
            Assert.Equal("var", model.GetTypeInfo(declaration2).Type.ToTestDisplayString());
            Assert.Equal(TypeKind.Class, model.GetTypeInfo(declaration2).Type.TypeKind);
            Assert.Null(model.GetSymbolInfo(declaration2).Symbol);

            Assert.Equal("var", declaration2.Type.ToString());
            Assert.Equal("var", model.GetSymbolInfo(declaration2.Type).Symbol.ToTestDisplayString());
            typeInfo = model.GetTypeInfo(declaration2.Type);
            Assert.Equal("var", typeInfo.Type.ToTestDisplayString());
            Assert.Equal(TypeKind.Class, typeInfo.Type.TypeKind);
            Assert.Equal(typeInfo.Type, typeInfo.ConvertedType);
            Assert.True(model.GetConversion(declaration2.Type).IsIdentity);
            Assert.Null(model.GetAliasInfo(declaration2.Type));
        }

        [Fact]
        public void OutVarDiscardInCtorInitializer()
        {
            var source =
    @"
public class C
{
    public C(out int i) { i = 1; System.Console.Write(""C ""); }
    static void Main()
    {
        new Derived2(out int i2);
        new Derived3(out int i3);
        new Derived4();
    }
}
public class Derived2 : C
{
    public Derived2(out int i) : base(out int _) { i = 2; System.Console.Write(""Derived2 ""); }
}
public class Derived3 : C
{
    public Derived3(out int i) : base(out var _) { i = 3; System.Console.Write(""Derived3 ""); }
}
public class Derived4 : C
{
    public Derived4(out int i) : base(out _) { i = 4; }
    public Derived4() : this(out _) { System.Console.Write(""Derived4""); }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics();
            CompileAndVerify(comp, expectedOutput: "C Derived2 C Derived3 C Derived4");
        }

        [Fact]
        public void DiscardNotRecognizedInOtherScenarios()
        {
            var source =
    @"
public class C
{
    void M<T>()
    {
        _.ToString();
        M(_);
        _<T>.ToString();
        (_<T>, _<T>) = (1, 2);
        M<_>();
        new C() { _ = 1 };
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugDll);
            comp.VerifyDiagnostics(
                // (6,9): error CS0103: The name '_' does not exist in the current context
                //         _.ToString();
                Diagnostic(ErrorCode.ERR_NameNotInContext, "_").WithArguments("_").WithLocation(6, 9),
                // (7,11): error CS0103: The name '_' does not exist in the current context
                //         M(_);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "_").WithArguments("_").WithLocation(7, 11),
                // (8,9): error CS0103: The name '_' does not exist in the current context
                //         _<T>.ToString();
                Diagnostic(ErrorCode.ERR_NameNotInContext, "_<T>").WithArguments("_").WithLocation(8, 9),
                // (9,10): error CS0103: The name '_' does not exist in the current context
                //         (_<T>, _<T>) = (1, 2);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "_<T>").WithArguments("_").WithLocation(9, 10),
                // (9,16): error CS0103: The name '_' does not exist in the current context
                //         (_<T>, _<T>) = (1, 2);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "_<T>").WithArguments("_").WithLocation(9, 16),
                // (10,11): error CS0246: The type or namespace name '_' could not be found (are you missing a using directive or an assembly reference?)
                //         M<_>();
                Diagnostic(ErrorCode.ERR_SingleTypeNameNotFound, "_").WithArguments("_").WithLocation(10, 11),
                // (11,19): error CS0117: 'C' does not contain a definition for '_'
                //         new C() { _ = 1 };
                Diagnostic(ErrorCode.ERR_NoSuchMember, "_").WithArguments("C", "_").WithLocation(11, 19)
                );
        }

        [Fact]
        public void TypedDiscardInMethodTypeInference()
        {
            var source =
    @"
public class C
{
    static void M<T>(out T t)
    {
        t = default(T);
        System.Console.Write(t.GetType().ToString());
    }
    static void Main()
    {
        M(out int _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics();
            CompileAndVerify(comp, expectedOutput: "System.Int32");
        }

        [Fact]
        public void UntypedDiscardInMethodTypeInference()
        {
            var source =
    @"
public class C
{
    static void M<T>(out T t)
    {
        t = default(T);
    }
    static void Main()
    {
        M(out var _);
        M(out _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics(
                // (10,9): error CS0411: The type arguments for method 'C.M<T>(out T)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
                //         M(out var _);
                Diagnostic(ErrorCode.ERR_CantInferMethTypeArgs, "M").WithArguments("C.M<T>(out T)").WithLocation(10, 9),
                // (11,9): error CS0411: The type arguments for method 'C.M<T>(out T)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
                //         M(out _);
                Diagnostic(ErrorCode.ERR_CantInferMethTypeArgs, "M").WithArguments("C.M<T>(out T)").WithLocation(11, 9)
                );
        }

        [Fact]
        public void PickOverloadWithTypedDiscard()
        {
            var source =
    @"
public class C
{
    static void M(out object x) { x = 1; System.Console.Write(""object returning M. ""); }
    static void M(out int x) { x = 2; System.Console.Write(""int returning M.""); }
    static void Main()
    {
        M(out object _);
        M(out int _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugExe);
            comp.VerifyDiagnostics();
            CompileAndVerify(comp, expectedOutput: "object returning M. int returning M.");
        }

        [Fact]
        public void CannotPickOverloadWithUntypedDiscard()
        {
            var source =
    @"
public class C
{
    static void M(out object x) { x = 1; }
    static void M(out int x) { x = 2; }
    static void Main()
    {
        M(out var _);
        M(out _);
        M(out byte _);
    }
}
";
            var comp = CreateCompilation(source, options: TestOptions.DebugDll);
            comp.VerifyDiagnostics(
                // (8,9): error CS0121: The call is ambiguous between the following methods or properties: 'C.M(out object)' and 'C.M(out int)'
                //         M(out var _);
                Diagnostic(ErrorCode.ERR_AmbigCall, "M").WithArguments("C.M(out object)", "C.M(out int)").WithLocation(8, 9),
                // (9,9): error CS0121: The call is ambiguous between the following methods or properties: 'C.M(out object)' and 'C.M(out int)'
                //         M(out _);
                Diagnostic(ErrorCode.ERR_AmbigCall, "M").WithArguments("C.M(out object)", "C.M(out int)").WithLocation(9, 9),
                // (10,15): error CS1503: Argument 1: cannot convert from 'out byte' to 'out object'
                //         M(out byte _);
                Diagnostic(ErrorCode.ERR_BadArgType, "byte _").WithArguments("1", "out byte", "out object").WithLocation(10, 15)
                );
        }

        [Fact]
        public void NoOverloadWithDiscard()
        {
            var source =
    @"
public class A { }
public class B : A
{
    static void M(A a)
    {
        a.M2(out A x);
        a.M2(out A _);
    }
}
public static class S
{
    public static void M2(this A self, out B x) { x = null; }
}";
            var comp = CreateCompilationWithMscorlib40(source, options: TestOptions.DebugDll, references: new[] { Net40.References.SystemCore });
            comp.VerifyDiagnostics(
                // (7,18): error CS1503: Argument 2: cannot convert from 'out A' to 'out B'
                //         a.M2(out A x);
                Diagnostic(ErrorCode.ERR_BadArgType, "A x").WithArguments("2", "out A", "out B").WithLocation(7, 18),
                // (8,18): error CS1503: Argument 2: cannot convert from 'out A' to 'out B'
                //         a.M2(out A _);
                Diagnostic(ErrorCode.ERR_BadArgType, "A _").WithArguments("2", "out A", "out B").WithLocation(8, 18)
                );
        }

        [Fact]
        [WorkItem(363727, "https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems/edit/363727")]
        public void FindCorrectBinderOnEmbeddedStatementWithMissingIdentifier()
        {
            var source =
    @"
public class C
{
    static void M(string x)
    {
        if(true)
            && int.TryParse(x, out int y)) id(iVal);
        // Note that the embedded statement is parsed as a missing identifier, followed by && with many spaces attached as leading trivia
    }
}";
            var comp = CreateCompilation(source, options: TestOptions.DebugDll);

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);
            var x = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(n => n.ToString() == "x").Single();
            Assert.Equal("x", x.ToString());
            Assert.Equal("System.String x", model.GetSymbolInfo(x).Symbol.ToTestDisplayString());
        }

        [Fact]
        public void DuplicateDeclarationInSwitchBlock()
        {
            var text = @"
public class C
{
    public static void Main(string[] args)
    {
        switch (args.Length)
        {
            case 0:
                M(M(out var x1), x1);
                M(M(out int x1), x1);
                break;
            case 1:
                M(M(out int x1), x1);
                break;
        }
    }
    static int M(out int z) => z = 1;
    static int M(int a, int b) => a+b;
}";
            var comp = CreateCompilationWithMscorlib461(text);
            comp.VerifyDiagnostics(
                // (10,29): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //                 M(M(out int x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(10, 29),
                // (13,29): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //                 M(M(out int x1), x1);
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(13, 29),
                // (13,34): error CS0165: Use of unassigned local variable 'x1'
                //                 M(M(out int x1), x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(13, 34)
                );
            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);
            var x6Decl = GetOutVarDeclarations(tree, "x1").ToArray();
            var x6Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(3, x6Decl.Length);
            Assert.Equal(3, x6Ref.Length);
            VerifyModelForOutVar(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[2]);
        }

        [Fact]
        public void DeclarationInLocalFunctionParameterDefault()
        {
            var text = @"
class C
{
    public static void Main(int arg)
    {
        void Local2(bool b = M(M(out int z1), z1), int s2 = z1) { var t = z1; }
        void Local5(bool b = M(M(out var z2), z2), int s2 = z2) { var t = z2; }

        int x = z1 + z2;
    }
    static int M(out int z) => z = 1;
    static bool M(int a, int b) => a+b == 0;
}
";
            // the scope of an expression variable introduced in the default expression
            // of a local function parameter is that default expression.
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (6,75): error CS0103: The name 'z1' does not exist in the current context
                //         void Local2(bool b = M(M(out int z1), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(6, 75),
                // (6,30): error CS1736: Default parameter value for 'b' must be a compile-time constant
                //         void Local2(bool b = M(M(out int z1), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M(M(out int z1), z1)").WithArguments("b").WithLocation(6, 30),
                // (6,61): error CS0103: The name 'z1' does not exist in the current context
                //         void Local2(bool b = M(M(out int z1), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(6, 61),
                // (7,75): error CS0103: The name 'z2' does not exist in the current context
                //         void Local5(bool b = M(M(out var z2), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(7, 75),
                // (7,30): error CS1736: Default parameter value for 'b' must be a compile-time constant
                //         void Local5(bool b = M(M(out var z2), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M(M(out var z2), z2)").WithArguments("b").WithLocation(7, 30),
                // (7,61): error CS0103: The name 'z2' does not exist in the current context
                //         void Local5(bool b = M(M(out var z2), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(7, 61),
                // (9,17): error CS0103: The name 'z1' does not exist in the current context
                //         int x = z1 + z2;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(9, 17),
                // (9,22): error CS0103: The name 'z2' does not exist in the current context
                //         int x = z1 + z2;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(9, 22),
                // (6,14): warning CS8321: The local function 'Local2' is declared but never used
                //         void Local2(bool b = M(M(out int z1), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Local2").WithArguments("Local2").WithLocation(6, 14),
                // (7,14): warning CS8321: The local function  'Local5' is declared but never used
                //         void Local5(bool b = M(M(out var z2), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Local5").WithArguments("Local5").WithLocation(7, 14)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(4, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, refs[0]);
                VerifyNotInScope(model, refs[1]);
                VerifyNotInScope(model, refs[2]);
                VerifyNotInScope(model, refs[3]);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void DeclarationInAnonymousMethodParameterDefault()
        {
            var text = @"
class C
{
    public static void Main(int arg)
    {
        System.Action<bool, int> d1 = delegate (
                                                bool b = M(M(out int z1), z1), 
                                                int s2 = z1) 
                                            { var t = z1; };
        System.Action<bool, int> d2 = delegate (
                                                bool b = M(M(out var z2), z2), 
                                                int s2 = z2)  
                                            { var t = z2; };

        int x = z1 + z2;
        d1 = d2 = null;
    }
    static int M(out int z) => z = 1;
    static int M(int a, int b) => a+b;
}
";
            // the scope of an expression variable introduced in the default expression
            // of a lambda parameter is that default expression.
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.GetDiagnostics().Verify(
                    // (7,56): error CS1065: Default values are not valid in this context.
                    //                                                 bool b = M(M(out int z1), z1), 
                    Diagnostic(ErrorCode.ERR_DefaultValueNotAllowed, "=").WithLocation(7, 56),
                    // (7,58): error CS1736: Default parameter value for 'b' must be a compile-time constant
                    //                                                 bool b = M(M(out int z1), z1), 
                    Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M(M(out int z1), z1)").WithArguments("b").WithLocation(7, 58),
                    // (8,56): error CS1065: Default values are not valid in this context.
                    //                                                 int s2 = z1) 
                    Diagnostic(ErrorCode.ERR_DefaultValueNotAllowed, "=").WithLocation(8, 56),
                    // (8,58): error CS0103: The name 'z1' does not exist in the current context
                    //                                                 int s2 = z1) 
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(8, 58),
                    // (9,55): error CS0103: The name 'z1' does not exist in the current context
                    //                                             { var t = z1; };
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(9, 55),
                    // (11,56): error CS1065: Default values are not valid in this context.
                    //                                                 bool b = M(M(out var z2), z2), 
                    Diagnostic(ErrorCode.ERR_DefaultValueNotAllowed, "=").WithLocation(11, 56),
                    // (11,58): error CS1736: Default parameter value for 'b' must be a compile-time constant
                    //                                                 bool b = M(M(out var z2), z2), 
                    Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M(M(out var z2), z2)").WithArguments("b").WithLocation(11, 58),
                    // (12,56): error CS1065: Default values are not valid in this context.
                    //                                                 int s2 = z2)  
                    Diagnostic(ErrorCode.ERR_DefaultValueNotAllowed, "=").WithLocation(12, 56),
                    // (12,58): error CS0103: The name 'z2' does not exist in the current context
                    //                                                 int s2 = z2)  
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(12, 58),
                    // (13,55): error CS0103: The name 'z2' does not exist in the current context
                    //                                             { var t = z2; };
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(13, 55),
                    // (15,17): error CS0103: The name 'z1' does not exist in the current context
                    //         int x = z1 + z2;
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(15, 17),
                    // (15,22): error CS0103: The name 'z2' does not exist in the current context
                    //         int x = z1 + z2;
                    Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(15, 22));

            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            var z1 = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "z1").First();
            Assert.Equal("System.Int32", model.GetTypeInfo(z1).Type.ToTestDisplayString());

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(4, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, refs[0]);
                VerifyNotInScope(model, refs[1]);
                VerifyNotInScope(model, refs[2]);
                VerifyNotInScope(model, refs[3]);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void Scope_LocalFunction_Attribute_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        void Local1(
            [Test(p = TakeOutParam(out int x3) && x3 > 0)]
            [Test(p = x4 && TakeOutParam(out int x4))]
            [Test(p = TakeOutParam(51, out int x5) && 
                      TakeOutParam(52, out int x5) && 
                      x5 > 0)]
            [Test(p1 = TakeOutParam(out int x6) && x6 > 0, 
                  p2 = TakeOutParam(out int x6) && x6 > 0)]
            [Test(p = TakeOutParam(out int x7) && x7 > 0)]
            [Test(p = x7 > 2)]
            int p1)
        {
            Dummy(x7, p1);
        }

        Local1(1);
    }

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public bool p {get; set;}
    public bool p1 {get; set;}
    public bool p2 {get; set;}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular9);
            compilation.GetDiagnostics().Where(d => d.Code != (int)ErrorCode.ERR_BadAttributeArgument).Verify(
                // (18,19): error CS0103: The name 'x7' does not exist in the current context
                //             Dummy(x7, p1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(18, 19),
                // (8,23): error CS0841: Cannot use local variable 'x4' before it is declared
                //             [Test(p = x4 && TakeOutParam(out int x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(8, 23),
                // (10,48): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                       TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(10, 48),
                // (13,45): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //                   p2 = TakeOutParam(out int x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(13, 45),
                // (15,23): error CS0103: The name 'x7' does not exist in the current context
                //             [Test(p = x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(15, 23)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_LocalFunction_Attribute_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        void Local1(
            [Test(TakeOutParam(out int x3) && x3 > 0)]
            [Test(x4 && TakeOutParam(out int x4))]
            [Test(TakeOutParam(51, out int x5) && 
                  TakeOutParam(52, out int x5) && 
                  x5 > 0)]
            [Test(TakeOutParam(out int x6) && x6 > 0, 
                  TakeOutParam(out int x6) && x6 > 0)]
            [Test(TakeOutParam(out int x7) && x7 > 0)]
            [Test(x7 > 2)]
            int p1)
        {
            Dummy(x7, p1);
        }

        Local1(1);
    }

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public Test(bool p) {}
    public Test(bool p1, bool p2) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular9);
            compilation.GetDiagnostics().Where(d => d.Code != (int)ErrorCode.ERR_BadAttributeArgument).Verify(
                // (18,19): error CS0103: The name 'x7' does not exist in the current context
                //             Dummy(x7, p1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(18, 19),
                // (8,19): error CS0841: Cannot use local variable 'x4' before it is declared
                //             [Test(x4 && TakeOutParam(out int x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(8, 19),
                // (10,44): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                   TakeOutParam(52, out int x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(10, 44),
                // (13,40): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //                   TakeOutParam(out int x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(13, 40),
                // (15,19): error CS0103: The name 'x7' does not exist in the current context
                //             [Test(x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(15, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_LocalFunction_Attribute_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        void Local1(
            [Test(p = TakeOutParam(out var x3) && x3 > 0)]
            [Test(p = x4 && TakeOutParam(out var x4))]
            [Test(p = TakeOutParam(51, out var x5) && 
                      TakeOutParam(52, out var x5) && 
                      x5 > 0)]
            [Test(p1 = TakeOutParam(out var x6) && x6 > 0, 
                  p2 = TakeOutParam(out var x6) && x6 > 0)]
            [Test(p = TakeOutParam(out var x7) && x7 > 0)]
            [Test(p = x7 > 2)]
            int p1)
        {
            Dummy(x7, p1);
        }

        Local1(1);
    }

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public bool p {get; set;}
    public bool p1 {get; set;}
    public bool p2 {get; set;}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular9);
            compilation.GetDiagnostics().Where(d => d.Code != (int)ErrorCode.ERR_BadAttributeArgument).Verify(
                // (18,19): error CS0103: The name 'x7' does not exist in the current context
                //             Dummy(x7, p1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(18, 19),
                // (8,23): error CS0841: Cannot use local variable 'x4' before it is declared
                //             [Test(p = x4 && TakeOutParam(out var x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(8, 23),
                // (10,48): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                       TakeOutParam(52, out var x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(10, 48),
                // (13,45): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //                   p2 = TakeOutParam(out var x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(13, 45),
                // (15,23): error CS0103: The name 'x7' does not exist in the current context
                //             [Test(p = x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(15, 23)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_LocalFunction_Attribute_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        void Local1(
            [Test(TakeOutParam(out var x3) && x3 > 0)]
            [Test(x4 && TakeOutParam(out var x4))]
            [Test(TakeOutParam(51, out var x5) && 
                  TakeOutParam(52, out var x5) && 
                  x5 > 0)]
            [Test(TakeOutParam(out var x6) && x6 > 0, 
                  TakeOutParam(out var x6) && x6 > 0)]
            [Test(TakeOutParam(out var x7) && x7 > 0)]
            [Test(x7 > 2)]
            int p1)
        {
            Dummy(x7, p1);
        }

        Local1(1);
    }

    bool Dummy(params object[] x) {return true;}

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
    static bool TakeOutParam(object y, out int x)
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public Test(bool p) {}
    public Test(bool p1, bool p2) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular9);
            compilation.GetDiagnostics().Where(d => d.Code != (int)ErrorCode.ERR_BadAttributeArgument).Verify(
                // (18,19): error CS0103: The name 'x7' does not exist in the current context
                //             Dummy(x7, p1);
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(18, 19),
                // (8,19): error CS0841: Cannot use local variable 'x4' before it is declared
                //             [Test(x4 && TakeOutParam(out var x4))]
                Diagnostic(ErrorCode.ERR_VariableUsedBeforeDeclaration, "x4").WithArguments("x4").WithLocation(8, 19),
                // (10,44): error CS0128: A local variable or function named 'x5' is already defined in this scope
                //                   TakeOutParam(52, out var x5) && 
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x5").WithArguments("x5").WithLocation(10, 44),
                // (13,40): error CS0128: A local variable or function named 'x6' is already defined in this scope
                //                   TakeOutParam(out var x6) && x6 > 0)]
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x6").WithArguments("x6").WithLocation(13, 40),
                // (15,19): error CS0103: The name 'x7' does not exist in the current context
                //             [Test(x7 > 2)]
                Diagnostic(ErrorCode.ERR_NameNotInContext, "x7").WithArguments("x7").WithLocation(15, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x3Decl = GetOutVarDeclaration(tree, "x3");
            var x3Ref = GetReference(tree, "x3");
            VerifyModelForOutVarInNotExecutableCode(model, x3Decl, x3Ref);

            var x4Decl = GetOutVarDeclaration(tree, "x4");
            var x4Ref = GetReference(tree, "x4");
            VerifyModelForOutVarInNotExecutableCode(model, x4Decl, x4Ref);

            var x5Decl = GetOutVarDeclarations(tree, "x5").ToArray();
            var x5Ref = GetReference(tree, "x5");
            Assert.Equal(2, x5Decl.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x5Decl[0], x5Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x5Decl[1]);

            var x6Decl = GetOutVarDeclarations(tree, "x6").ToArray();
            var x6Ref = GetReferences(tree, "x6").ToArray();
            Assert.Equal(2, x6Decl.Length);
            Assert.Equal(2, x6Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x6Decl[0], x6Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x6Decl[1]);

            var x7Decl = GetOutVarDeclaration(tree, "x7");
            var x7Ref = GetReferences(tree, "x7").ToArray();
            Assert.Equal(3, x7Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x7Decl, x7Ref[0]);
            VerifyNotInScope(model, x7Ref[1]);
            VerifyNotInScope(model, x7Ref[2]);
        }

        [Fact]
        public void Scope_LocalFunction_Attribute_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        TakeOutParam(out var x1);
        TakeOutParam(out var x2);

        void Local1(
            [Test(p = TakeOutParam(out int x2) && x1 > 0 && x2 > 0)]
            int p1)
        {
            p1 = 0;
        }

        Local1(x2);
    }

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public bool p {get; set;}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular9);
            compilation.GetDiagnostics().Where(d => d.Code != (int)ErrorCode.ERR_BadAttributeArgument).Verify(
                // (10,44): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             [Test(p = TakeOutParam(out int x2) && x1 > 0 && x2 > 0)]
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(10, 44)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVarInNotExecutableCode(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref[1]);
            VerifyModelForOutVarInNotExecutableCode(model, x2Decl[1], x2Ref[0]);
        }

        [Fact]
        public void Scope_LocalFunction_Attribute_06()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        TakeOutParam(out var x1);
        TakeOutParam(out var x2);

        void Local1(
            [Test(TakeOutParam(out int x2) && x1 > 0 && x2 > 0)]
            int p1)
        {
            p1 = 0;
        }

        Local1(x2);
    }

    static bool TakeOutParam(out int x) 
    {
        x = 123;
        return true;
    }
}

class Test : System.Attribute
{
    public Test(bool p) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular9);
            compilation.GetDiagnostics().Where(d => d.Code != (int)ErrorCode.ERR_BadAttributeArgument).Verify(
                // (10,40): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //             [Test(TakeOutParam(out int x2) && x1 > 0 && x2 > 0)]
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(10, 40)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclaration(tree, "x1");
            var x1Ref = GetReference(tree, "x1");
            VerifyModelForOutVarInNotExecutableCode(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").ToArray();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Decl.Length);
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVar(model, x2Decl[0], x2Ref[1]);
            VerifyModelForOutVarInNotExecutableCode(model, x2Decl[1], x2Ref[0]);
        }

        [Fact]
        public void Scope_InvalidArrayDimensions01()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        int x1 = 0;
        int[Test1(out int x1), x1] _1;
        int[Test1(out int x2), x2] x2;
    }

    static int Test1(out int x)
    {
        x = 1;
        return 1;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (7,12): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         int[Test1(out int x1), x1] _1;
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[Test1(out int x1), x1]").WithLocation(7, 12),
                // (7,27): error CS0128: A local variable or function named 'x1' is already defined in this scope
                //         int[Test1(out int x1), x1] _1;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x1").WithArguments("x1").WithLocation(7, 27),
                // (8,12): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         int[Test1(out int x2), x2] x2;
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[Test1(out int x2), x2]").WithLocation(8, 12),
                // (8,36): error CS0128: A local variable or function named 'x2' is already defined in this scope
                //         int[Test1(out int x2), x2] x2;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(8, 36),
                // (6,13): warning CS0219: The variable 'x1' is assigned but its value is never used
                //         int x1 = 0;
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "x1").WithArguments("x1").WithLocation(6, 13),
                // (7,27): warning CS0168: The variable 'x1' is declared but never used
                //         int[Test1(out int x1), x1] _1;
                Diagnostic(ErrorCode.WRN_UnreferencedVar, "x1").WithArguments("x1").WithLocation(7, 27),
                // (7,36): warning CS0168: The variable '_1' is declared but never used
                //         int[Test1(out int x1), x1] _1;
                Diagnostic(ErrorCode.WRN_UnreferencedVar, "_1").WithArguments("_1").WithLocation(7, 36),
                // (8,27): warning CS0168: The variable 'x2' is declared but never used
                //         int[Test1(out int x2), x2] x2;
                Diagnostic(ErrorCode.WRN_UnreferencedVar, "x2").WithArguments("x2").WithLocation(8, 27),
                // (8,36): warning CS0168: The variable 'x2' is declared but never used
                //         int[Test1(out int x2), x2] x2;
                Diagnostic(ErrorCode.WRN_UnreferencedVar, "x2").WithArguments("x2").WithLocation(8, 36)
            );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").Single();
            VerifyNotAnOutLocal(model, x1Ref);
            VerifyModelForOutVarDuplicateInSameScope(model, x1Decl);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").Single();
            VerifyModelForOutVarInNotExecutableCode(model, x2Decl, x2Ref);
        }

        [Fact]
        public void Scope_InvalidArrayDimensions_02()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(object x) {return null;}

    void Test1()
    {
        using (int[] d = null)
        {
            Dummy(x1);
        }
    }

    void Test2()
    {
        using (int[] d = null)
            Dummy(x2);
    }

    void Test3()
    {
        var x3 = 11;
        Dummy(x3);

        using (int[] d = null)
            Dummy(x3);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";
            // replace 'int[]'  with 'int[TakeOutParam(true, out var x1), x1]'
            var syntaxTree = Parse(source, filename: "file.cs");
            for (int i = 0; i < 3; i++)
            {
                var method = syntaxTree.GetCompilationUnitRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().ElementAt(i + 2);
                var rankSpecifierOld = method.DescendantNodes().OfType<ArrayRankSpecifierSyntax>().Single();
                {
                    var rankSpecifierNew = rankSpecifierOld
                        .WithSizes(SyntaxFactory.SeparatedList<ExpressionSyntax>(
                            SyntaxFactory.NodeOrTokenList(
                                SyntaxFactory.ParseExpression($"TakeOutParam(true, out var x{i + 1})"),
                                SyntaxFactory.Token(SyntaxKind.CommaToken),
                                SyntaxFactory.ParseExpression($"x{i + 1}")
                                )));
                    syntaxTree = syntaxTree.GetCompilationUnitRoot().ReplaceNode(rankSpecifierOld, rankSpecifierNew).SyntaxTree;
                }
            }

            var compilation = CreateCompilation(syntaxTree, options: TestOptions.ReleaseExe);

            compilation.VerifyDiagnostics(
                // file.cs(12,16): error CS1674: 'int[*,*]': type used in a using statement must implement 'System.IDisposable'.
                //         using (int[TakeOutParam(true, out var x1),x1] d = null)
                Diagnostic(ErrorCode.ERR_NoConvToIDisp, "int[TakeOutParam(true, out var x1),x1] d = null").WithArguments("int[*,*]").WithLocation(12, 16),
                // file.cs(12,19): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         using (int[TakeOutParam(true, out var x1),x1] d = null)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x1),x1]").WithLocation(12, 19),
                // file.cs(12,20): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using (int[TakeOutParam(true, out var x1),x1] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x1)").WithArguments("bool", "int").WithLocation(12, 20),
                // file.cs(12,51): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using (int[TakeOutParam(true, out var x1),x1] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x1").WithArguments("bool", "int").WithLocation(12, 51),
                // file.cs(14,19): error CS0165: Use of unassigned local variable 'x1'
                //             Dummy(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(14, 19),
                // file.cs(20,16): error CS1674: 'int[*,*]': type used in a using statement must implement 'System.IDisposable'.
                //         using (int[TakeOutParam(true, out var x2),x2] d = null)
                Diagnostic(ErrorCode.ERR_NoConvToIDisp, "int[TakeOutParam(true, out var x2),x2] d = null").WithArguments("int[*,*]").WithLocation(20, 16),
                // file.cs(20,19): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         using (int[TakeOutParam(true, out var x2),x2] d = null)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x2),x2]").WithLocation(20, 19),
                // file.cs(20,20): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using (int[TakeOutParam(true, out var x2),x2] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x2)").WithArguments("bool", "int").WithLocation(20, 20),
                // file.cs(20,51): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using (int[TakeOutParam(true, out var x2),x2] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x2").WithArguments("bool", "int").WithLocation(20, 51),
                // file.cs(21,19): error CS0165: Use of unassigned local variable 'x2'
                //             Dummy(x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(21, 19),
                // file.cs(29,16): error CS1674: 'int[*,*]': type used in a using statement must implement 'System.IDisposable'.
                //         using (int[TakeOutParam(true, out var x3),x3] d = null)
                Diagnostic(ErrorCode.ERR_NoConvToIDisp, "int[TakeOutParam(true, out var x3),x3] d = null").WithArguments("int[*,*]").WithLocation(29, 16),
                // file.cs(29,19): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         using (int[TakeOutParam(true, out var x3),x3] d = null)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x3),x3]").WithLocation(29, 19),
                // file.cs(29,20): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using (int[TakeOutParam(true, out var x3),x3] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x3)").WithArguments("bool", "int").WithLocation(29, 20),
                // file.cs(29,47): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         using (int[TakeOutParam(true, out var x3),x3] d = null)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(29, 47),
                // file.cs(29,51): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using (int[TakeOutParam(true, out var x3),x3] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x3").WithArguments("bool", "int").WithLocation(29, 51),
                // file.cs(30,19): error CS0165: Use of unassigned local variable 'x3'
                //             Dummy(x3);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x3").WithArguments("x3").WithLocation(30, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(3, x3Ref.Length);
            VerifyNotAnOutLocal(model, x3Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x3Decl, x3Ref[1], x3Ref[2]);
        }

        [Fact]
        public void Scope_InvalidArrayDimensions_03()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(object x) {return null;}

    void Test1()
    {
        using int[TakeOutParam(true, out var x1), x1] d = null;
        Dummy(x1);
    }

    void Test2()
    {
        var x2 = 11;
        Dummy(x2);

        using int[TakeOutParam(true, out var x2), x2] d = null;
        Dummy(x2);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilation(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (12,9): error CS1674: 'int[*,*]': type used in a using statement must implement 'System.IDisposable'.
                //         using int[TakeOutParam(true, out var x1), x1] d = null;
                Diagnostic(ErrorCode.ERR_NoConvToIDisp, "using int[TakeOutParam(true, out var x1), x1] d = null;").WithArguments("int[*,*]").WithLocation(12, 9),
                // (12,18): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         using int[TakeOutParam(true, out var x1), x1] d = null;
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x1), x1]").WithLocation(12, 18),
                // (12,19): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using int[TakeOutParam(true, out var x1), x1] d = null;
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x1)").WithArguments("bool", "int").WithLocation(12, 19),
                // (12,51): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using int[TakeOutParam(true, out var x1), x1] d = null;
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x1").WithArguments("bool", "int").WithLocation(12, 51),
                // (13,15): error CS0165: Use of unassigned local variable 'x1'
                //         Dummy(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(13, 15),
                // (21,9): error CS1674: 'int[*,*]': type used in a using statement must implement 'System.IDisposable'.
                //         using int[TakeOutParam(true, out var x2), x2] d = null;
                Diagnostic(ErrorCode.ERR_NoConvToIDisp, "using int[TakeOutParam(true, out var x2), x2] d = null;").WithArguments("int[*,*]").WithLocation(21, 9),
                // (21,18): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         using int[TakeOutParam(true, out var x2), x2] d = null;
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x2), x2]").WithLocation(21, 18),
                // (21,19): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         using int[TakeOutParam(true, out var x2), x2] d = null;
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x2)").WithArguments("bool", "int").WithLocation(21, 19),
                // (21,46): error CS0128: A local variable or function named 'x2' is already defined in this scope
                //         using int[TakeOutParam(true, out var x2), x2] d = null;
                Diagnostic(ErrorCode.ERR_LocalDuplicate, "x2").WithArguments("x2").WithLocation(21, 46),
                // (21,46): warning CS0168: The variable 'x2' is declared but never used
                //         using int[TakeOutParam(true, out var x2), x2] d = null;
                Diagnostic(ErrorCode.WRN_UnreferencedVar, "x2").WithArguments("x2").WithLocation(21, 46)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(3, x2Ref.Length);
            VerifyNotAnOutLocal(model, x2Ref[0]);
            VerifyNotAnOutLocal(model, x2Ref[1]);
            VerifyNotAnOutLocal(model, x2Ref[2]);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl, isShadowed: true);
        }

        [Fact]
        public void Scope_InvalidArrayDimensions_04()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    bool Dummy(object x) {return true;}

    void Test1()
    {
        for (int[] a = null;;)
            Dummy(x1);
    }

    void Test2()
    {
        var x2 = 11;
        Dummy(x2);

        for (int[] a = null;;)
            Dummy(x2);
    }

    static bool TakeOutParam(object y, out bool x) 
    {
        x = true;
        return true;
    }
}
";
            // replace 'int[]'  with 'int[TakeOutParam(true, out var x1), x1]'
            var syntaxTree = Parse(source, filename: "file.cs");
            for (int i = 0; i < 2; i++)
            {
                var method = syntaxTree.GetCompilationUnitRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().ElementAt(i + 2);
                var rankSpecifierOld = method.DescendantNodes().OfType<ArrayRankSpecifierSyntax>().Single();
                {
                    var rankSpecifierNew = rankSpecifierOld
                        .WithSizes(SyntaxFactory.SeparatedList<ExpressionSyntax>(
                            SyntaxFactory.NodeOrTokenList(
                                SyntaxFactory.ParseExpression($"TakeOutParam(true, out var x{i + 1})"),
                                SyntaxFactory.Token(SyntaxKind.CommaToken),
                                SyntaxFactory.ParseExpression($"x{i + 1}")
                            )));
                    syntaxTree = syntaxTree.GetCompilationUnitRoot().ReplaceNode(rankSpecifierOld, rankSpecifierNew).SyntaxTree;
                }
            }

            var compilation = CreateCompilation(syntaxTree, options: TestOptions.DebugExe);
            compilation.VerifyDiagnostics(
                // file.cs(12,17): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         for (int[TakeOutParam(true, out var x1),x1] a = null;;)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x1),x1]").WithLocation(12, 17),
                // file.cs(12,18): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         for (int[TakeOutParam(true, out var x1),x1] a = null;;)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x1)").WithArguments("bool", "int").WithLocation(12, 18),
                // file.cs(12,49): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         for (int[TakeOutParam(true, out var x1),x1] a = null;;)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x1").WithArguments("bool", "int").WithLocation(12, 49),
                // file.cs(13,19): error CS0165: Use of unassigned local variable 'x1'
                //             Dummy(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(13, 19),
                // file.cs(12,53): warning CS0219: The variable 'a' is assigned but its value is never used
                //         for (int[TakeOutParam(true, out var x1),x1] a = null;;)
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "a").WithArguments("a").WithLocation(12, 53),
                // file.cs(21,17): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         for (int[TakeOutParam(true, out var x2),x2] a = null;;)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x2),x2]").WithLocation(21, 17),
                // file.cs(21,45): error CS0136: A local or parameter named 'x2' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         for (int[TakeOutParam(true, out var x2),x2] a = null;;)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x2").WithArguments("x2").WithLocation(21, 45),
                // file.cs(21,18): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         for (int[TakeOutParam(true, out var x2),x2] a = null;;)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x2)").WithArguments("bool", "int").WithLocation(21, 18),
                // file.cs(21,49): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         for (int[TakeOutParam(true, out var x2),x2] a = null;;)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x2").WithArguments("bool", "int").WithLocation(21, 49),
                // file.cs(22,19): error CS0165: Use of unassigned local variable 'x2'
                //             Dummy(x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(22, 19),
                // file.cs(21,53): warning CS0219: The variable 'a' is assigned but its value is never used
                //         for (int[TakeOutParam(true, out var x2),x2] a = null;;)
                Diagnostic(ErrorCode.WRN_UnreferencedVarAssg, "a").WithArguments("a").WithLocation(21, 53)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVarInNotExecutableCode(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(3, x2Ref.Length);
            VerifyNotAnOutLocal(model, x2Ref[0]);
            VerifyModelForOutVarInNotExecutableCode(model, x2Decl, x2Ref[1], x2Ref[2]);
        }

        [Fact]
        public void Scope_InvalidArrayDimensions_05()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
    }

    System.IDisposable Dummy(object x) {return null;}

    unsafe void Test1()
    {
        fixed (int[TakeOutParam(true, out var x1), x1] d = null)
        {
            Dummy(x1);
        }
    }

    unsafe void Test2()
    {
        fixed (int[TakeOutParam(true, out var x2), x2] d = null)
            Dummy(x2);
    }

    unsafe void Test3()
    {
        var x3 = 11;
        Dummy(x3);

        fixed (int[TakeOutParam(true, out var x3), x3] d = null)
            Dummy(x3);
    }

    static bool TakeOutParam<T>(T y, out T x) 
    {
        x = y;
        return true;
    }
}
";

            var compilation = CreateCompilation(source, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (10,17): error CS0227: Unsafe code may only appear if compiling with /unsafe
                //     unsafe void Test1()
                Diagnostic(ErrorCode.ERR_IllegalUnsafe, "Test1").WithLocation(10, 17),
                // (12,19): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         fixed (int[TakeOutParam(true, out var x1), x1] d = null)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x1), x1]").WithLocation(12, 19),
                // (12,20): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         fixed (int[TakeOutParam(true, out var x1), x1] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x1)").WithArguments("bool", "int").WithLocation(12, 20),
                // (12,52): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         fixed (int[TakeOutParam(true, out var x1), x1] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x1").WithArguments("bool", "int").WithLocation(12, 52),
                // (12,56): error CS0209: The type of a local declared in a fixed statement must be a pointer type
                //         fixed (int[TakeOutParam(true, out var x1), x1] d = null)
                Diagnostic(ErrorCode.ERR_BadFixedInitType, "d = null").WithLocation(12, 56),
                // (14,19): error CS0165: Use of unassigned local variable 'x1'
                //             Dummy(x1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x1").WithArguments("x1").WithLocation(14, 19),
                // (18,17): error CS0227: Unsafe code may only appear if compiling with /unsafe
                //     unsafe void Test2()
                Diagnostic(ErrorCode.ERR_IllegalUnsafe, "Test2").WithLocation(18, 17),
                // (20,19): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         fixed (int[TakeOutParam(true, out var x2), x2] d = null)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x2), x2]").WithLocation(20, 19),
                // (20,20): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         fixed (int[TakeOutParam(true, out var x2), x2] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x2)").WithArguments("bool", "int").WithLocation(20, 20),
                // (20,52): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         fixed (int[TakeOutParam(true, out var x2), x2] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x2").WithArguments("bool", "int").WithLocation(20, 52),
                // (20,56): error CS0209: The type of a local declared in a fixed statement must be a pointer type
                //         fixed (int[TakeOutParam(true, out var x2), x2] d = null)
                Diagnostic(ErrorCode.ERR_BadFixedInitType, "d = null").WithLocation(20, 56),
                // (21,19): error CS0165: Use of unassigned local variable 'x2'
                //             Dummy(x2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x2").WithArguments("x2").WithLocation(21, 19),
                // (24,17): error CS0227: Unsafe code may only appear if compiling with /unsafe
                //     unsafe void Test3()
                Diagnostic(ErrorCode.ERR_IllegalUnsafe, "Test3").WithLocation(24, 17),
                // (29,19): error CS0270: Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)
                //         fixed (int[TakeOutParam(true, out var x3), x3] d = null)
                Diagnostic(ErrorCode.ERR_ArraySizeInDeclaration, "[TakeOutParam(true, out var x3), x3]").WithLocation(29, 19),
                // (29,20): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         fixed (int[TakeOutParam(true, out var x3), x3] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "TakeOutParam(true, out var x3)").WithArguments("bool", "int").WithLocation(29, 20),
                // (29,47): error CS0136: A local or parameter named 'x3' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
                //         fixed (int[TakeOutParam(true, out var x3), x3] d = null)
                Diagnostic(ErrorCode.ERR_LocalIllegallyOverrides, "x3").WithArguments("x3").WithLocation(29, 47),
                // (29,52): error CS0029: Cannot implicitly convert type 'bool' to 'int'
                //         fixed (int[TakeOutParam(true, out var x3), x3] d = null)
                Diagnostic(ErrorCode.ERR_NoImplicitConv, "x3").WithArguments("bool", "int").WithLocation(29, 52),
                // (29,56): error CS0209: The type of a local declared in a fixed statement must be a pointer type
                //         fixed (int[TakeOutParam(true, out var x3), x3] d = null)
                Diagnostic(ErrorCode.ERR_BadFixedInitType, "d = null").WithLocation(29, 56),
                // (30,19): error CS0165: Use of unassigned local variable 'x3'
                //             Dummy(x3);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "x3").WithArguments("x3").WithLocation(30, 19)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var x1Decl = GetOutVarDeclarations(tree, "x1").Single();
            var x1Ref = GetReferences(tree, "x1").ToArray();
            Assert.Equal(2, x1Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x1Decl, x1Ref);

            var x2Decl = GetOutVarDeclarations(tree, "x2").Single();
            var x2Ref = GetReferences(tree, "x2").ToArray();
            Assert.Equal(2, x2Ref.Length);
            VerifyModelForOutVarWithoutDataFlow(model, x2Decl, x2Ref);

            var x3Decl = GetOutVarDeclarations(tree, "x3").Single();
            var x3Ref = GetReferences(tree, "x3").ToArray();
            Assert.Equal(3, x3Ref.Length);
            VerifyNotAnOutLocal(model, x3Ref[0]);
            VerifyModelForOutVarWithoutDataFlow(model, x3Decl, x3Ref[1], x3Ref[2]);
        }

        [Fact]
        public void DeclarationInNameof_00()
        {
            var text = @"
class C
{
    public static void Main()
    {
        var x = nameof(M2(M1(out var x1), x1)).ToString();
    }
    static int M1(out int z) => z = 1;
    static int M2(int a, int b) => 2;
}
";
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (6,24): error CS8081: Expression does not have a name.
                //         var x = nameof(M2(M1(out var x1), x1)).ToString();
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M2(M1(out var x1), x1)").WithLocation(6, 24)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            var name = "x1";
            var decl = GetOutVarDeclaration(tree, name);
            var refs = GetReferences(tree, name).ToArray();
            Assert.Equal(1, refs.Length);
            VerifyModelForOutVarInNotExecutableCode(model, decl, refs);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        public void DeclarationInNameof_01()
        {
            var text = @"
class C
{
    public static void Main(int arg)
    {
        void Local2(bool b = M(nameof(M(out int z1)), z1), int s2 = z1) { var t = z1; }
        void Local5(bool b = M(nameof(M(out var z2)), z2), int s2 = z2) { var t = z2; }

        int x = z1 + z2;
    }
    static int M(out int z) => z = 1;
    static bool M(object a, int b) => b == 0;
}
";
            // the scope of an expression variable introduced in the default expression
            // of a local function parameter is that default expression.
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (6,83): error CS0103: The name 'z1' does not exist in the current context
                //         void Local2(bool b = M(nameof(M(out int z1)), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(6, 83),
                // (6,39): error CS8081: Expression does not have a name.
                //         void Local2(bool b = M(nameof(M(out int z1)), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out int z1)").WithLocation(6, 39),
                // (6,30): error CS1736: Default parameter value for 'b' must be a compile-time constant
                //         void Local2(bool b = M(nameof(M(out int z1)), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M(nameof(M(out int z1)), z1)").WithArguments("b").WithLocation(6, 30),
                // (6,69): error CS0103: The name 'z1' does not exist in the current context
                //         void Local2(bool b = M(nameof(M(out int z1)), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(6, 69),
                // (7,83): error CS0103: The name 'z2' does not exist in the current context
                //         void Local5(bool b = M(nameof(M(out var z2)), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(7, 83),
                // (7,39): error CS8081: Expression does not have a name.
                //         void Local5(bool b = M(nameof(M(out var z2)), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out var z2)").WithLocation(7, 39),
                // (7,30): error CS1736: Default parameter value for 'b' must be a compile-time constant
                //         void Local5(bool b = M(nameof(M(out var z2)), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M(nameof(M(out var z2)), z2)").WithArguments("b").WithLocation(7, 30),
                // (7,69): error CS0103: The name 'z2' does not exist in the current context
                //         void Local5(bool b = M(nameof(M(out var z2)), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(7, 69),
                // (9,17): error CS0103: The name 'z1' does not exist in the current context
                //         int x = z1 + z2;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(9, 17),
                // (9,22): error CS0103: The name 'z2' does not exist in the current context
                //         int x = z1 + z2;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(9, 22),
                // (6,55): error CS0165: Use of unassigned local variable 'z1'
                //         void Local2(bool b = M(nameof(M(out int z1)), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.ERR_UseDefViolation, "z1").WithArguments("z1").WithLocation(6, 55),
                // (7,55): error CS0165: Use of unassigned local variable 'z2'
                //         void Local5(bool b = M(nameof(M(out var z2)), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.ERR_UseDefViolation, "z2").WithArguments("z2").WithLocation(7, 55),
                // (6,14): warning CS8321: The local function 'Local2' is declared but never used
                //         void Local2(bool b = M(nameof(M(out int z1)), z1), int s2 = z1) { var t = z1; }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Local2").WithArguments("Local2").WithLocation(6, 14),
                // (7,14): warning CS8321: The local function 'Local5' is declared but never used
                //         void Local5(bool b = M(nameof(M(out var z2)), z2), int s2 = z2) { var t = z2; }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Local5").WithArguments("Local5").WithLocation(7, 14)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(4, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, reference: refs[0]);
                VerifyNotInScope(model, refs[1]);
                VerifyNotInScope(model, refs[2]);
                VerifyNotInScope(model, refs[3]);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void DeclarationInNameof_02a()
        {
            var text = @"
[My(C.M(nameof(C.M(out int z1)), z1), z1)]
[My(C.M(nameof(C.M(out var z2)), z2), z2)]
class C
{
    public static int M(out int z) => z = 1;
    public static bool M(object a, int b) => b == 0;
}
class MyAttribute: System.Attribute
{
    public MyAttribute(bool x, int y) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (2,16): error CS8081: Expression does not have a name.
                // [My(C.M(nameof(C.M(out int z1)), z1), z1)]
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "C.M(out int z1)").WithLocation(2, 16),
                // (2,5): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [My(C.M(nameof(C.M(out int z1)), z1), z1)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "C.M(nameof(C.M(out int z1)), z1)").WithLocation(2, 5),
                // (2,39): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [My(C.M(nameof(C.M(out int z1)), z1), z1)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "z1").WithLocation(2, 39),
                // (3,16): error CS8081: Expression does not have a name.
                // [My(C.M(nameof(C.M(out var z2)), z2), z2)]
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "C.M(out var z2)").WithLocation(3, 16),
                // (3,5): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [My(C.M(nameof(C.M(out var z2)), z2), z2)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "C.M(nameof(C.M(out var z2)), z2)").WithLocation(3, 5),
                // (3,39): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [My(C.M(nameof(C.M(out var z2)), z2), z2)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "z2").WithLocation(3, 39)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(2, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, refs);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void DeclarationInNameof_02b()
        {
            var text1 = @"
[assembly: My(C.M(nameof(C.M(out int z1)), z1), z1)]
[assembly: My(C.M(nameof(C.M(out var z2)), z2), z2)]
";
            var text2 = @"
class C
{
    public static int M(out int z) => z = 1;
    public static bool M(object a, int b) => b == 0;
}
class MyAttribute: System.Attribute
{
    public MyAttribute(bool x, int y) {}
}
";
            var compilation = CreateCompilationWithMscorlib461(new[] { text1, text2 });
            compilation.VerifyDiagnostics(
                // (2,26): error CS8081: Expression does not have a name.
                // [assembly: My(C.M(nameof(C.M(out int z1)), z1), z1)]
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "C.M(out int z1)").WithLocation(2, 26),
                // (2,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [assembly: My(C.M(nameof(C.M(out int z1)), z1), z1)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "C.M(nameof(C.M(out int z1)), z1)").WithLocation(2, 15),
                // (2,49): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [assembly: My(C.M(nameof(C.M(out int z1)), z1), z1)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "z1").WithLocation(2, 49),
                // (3,26): error CS8081: Expression does not have a name.
                // [assembly: My(C.M(nameof(C.M(out var z2)), z2), z2)]
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "C.M(out var z2)").WithLocation(3, 26),
                // (3,15): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [assembly: My(C.M(nameof(C.M(out var z2)), z2), z2)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "C.M(nameof(C.M(out var z2)), z2)").WithLocation(3, 15),
                // (3,49): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                // [assembly: My(C.M(nameof(C.M(out var z2)), z2), z2)]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "z2").WithLocation(3, 49)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(2, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, refs);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void DeclarationInNameof_03()
        {
            var text = @"
class C
{
    public static void Main(string[] args)
    {
        switch ((object)args.Length)
        {
            case !M(nameof(M(out int z1)), z1):
                System.Console.WriteLine(z1);
                break;
            case !M(nameof(M(out var z2)), z2):
                System.Console.WriteLine(z2);
                break;
        }
    }
    public static int M(out int z) => z = 1;
    public static bool M(object a, int b) => b == 0;
}
";
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (8,28): error CS8081: Expression does not have a name.
                //             case !M(nameof(M(out int z1)), z1):
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out int z1)").WithLocation(8, 28),
                // (8,18): error CS0150: A constant value is expected
                //             case !M(nameof(M(out int z1)), z1):
                Diagnostic(ErrorCode.ERR_ConstantExpected, "!M(nameof(M(out int z1)), z1)").WithLocation(8, 18),
                // (11,28): error CS8081: Expression does not have a name.
                //             case !M(nameof(M(out var z2)), z2):
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out var z2)").WithLocation(11, 28),
                // (11,18): error CS0150: A constant value is expected
                //             case !M(nameof(M(out var z2)), z2):
                Diagnostic(ErrorCode.ERR_ConstantExpected, "!M(nameof(M(out var z2)), z2)").WithLocation(11, 18),
                // (8,44): error CS0165: Use of unassigned local variable 'z1'
                //             case !M(nameof(M(out int z1)), z1):
                Diagnostic(ErrorCode.ERR_UseDefViolation, "z1").WithArguments("z1").WithLocation(8, 44),
                // (11,44): error CS0165: Use of unassigned local variable 'z2'
                //             case !M(nameof(M(out var z2)), z2):
                Diagnostic(ErrorCode.ERR_UseDefViolation, "z2").WithArguments("z2").WithLocation(11, 44)
            );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(2, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, refs);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void DeclarationInNameof_04()
        {
            var text = @"
class C
{
    const bool a = M(nameof(M(out int z1)), z1);
    const bool b = M(nameof(M(out var z2)), z2);
    const bool c = (z1 + z2) == 0;

    public static int M(out int z) => z = 1;
    public static bool M(object a, int b) => b == 0;
}
";
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (5,29): error CS8081: Expression does not have a name.
                //     const bool b = M(nameof(M(out var z2)), z2);
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out var z2)").WithLocation(5, 29),
                // (5,20): error CS0133: The expression being assigned to 'C.b' must be constant
                //     const bool b = M(nameof(M(out var z2)), z2);
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "M(nameof(M(out var z2)), z2)").WithArguments("C.b").WithLocation(5, 20),
                // (6,21): error CS0103: The name 'z1' does not exist in the current context
                //     const bool c = (z1 + z2) == 0;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(6, 21),
                // (6,26): error CS0103: The name 'z2' does not exist in the current context
                //     const bool c = (z1 + z2) == 0;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z2").WithArguments("z2").WithLocation(6, 26),
                // (4,29): error CS8081: Expression does not have a name.
                //     const bool a = M(nameof(M(out int z1)), z1);
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out int z1)").WithLocation(4, 29),
                // (4,20): error CS0133: The expression being assigned to 'C.a' must be constant
                //     const bool a = M(nameof(M(out int z1)), z1);
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "M(nameof(M(out int z1)), z1)").WithArguments("C.a").WithLocation(4, 20)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(2, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, refs[0]);
                VerifyNotInScope(model, refs[1]);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void DeclarationInNameof_05()
        {
            var text = @"
class C
{
    public static void Main(string[] args)
    {
        const bool a = M(nameof(M(out int z1)), z1);
        const bool b = M(nameof(M(out var z2)), z2);
        bool c = (z1 + z2) == 0;
    }

    public static int M(out int z) => z = 1;
    public static bool M(object a, int b) => b == 0;
}
";
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (6,33): error CS8081: Expression does not have a name.
                //         const bool a = M(nameof(M(out int z1)), z1);
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out int z1)").WithLocation(6, 33),
                // (6,24): error CS0133: The expression being assigned to 'a' must be constant
                //         const bool a = M(nameof(M(out int z1)), z1);
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "M(nameof(M(out int z1)), z1)").WithArguments("a").WithLocation(6, 24),
                // (7,33): error CS8081: Expression does not have a name.
                //         const bool b = M(nameof(M(out var z2)), z2);
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "M(out var z2)").WithLocation(7, 33),
                // (7,24): error CS0133: The expression being assigned to 'b' must be constant
                //         const bool b = M(nameof(M(out var z2)), z2);
                Diagnostic(ErrorCode.ERR_NotConstantExpression, "M(nameof(M(out var z2)), z2)").WithArguments("b").WithLocation(7, 24),
                // (6,49): error CS0165: Use of unassigned local variable 'z1'
                //         const bool a = M(nameof(M(out int z1)), z1);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "z1").WithArguments("z1").WithLocation(6, 49),
                // (7,49): error CS0165: Use of unassigned local variable 'z2'
                //         const bool b = M(nameof(M(out var z2)), z2);
                Diagnostic(ErrorCode.ERR_UseDefViolation, "z2").WithArguments("z2").WithLocation(7, 49)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            for (int i = 1; i <= 2; i++)
            {
                var name = $"z{i}";
                var decl = GetOutVarDeclaration(tree, name);
                var refs = GetReferences(tree, name).ToArray();
                Assert.Equal(2, refs.Length);
                VerifyModelForOutVarInNotExecutableCode(model, decl, refs);
                var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
                Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
            }
        }

        [Fact]
        public void DeclarationInNameof_06()
        {
            var text = @"
class C
{
    public static void Main(string[] args)
    {
        string s = nameof((System.Action)(() => M(M(out var z1), z1))).ToString();
        bool c = z1 == 0;
    }

    public static int M(out int z) => z = 1;
    public static bool M(object a, int b) => b == 0;
}
";
            var compilation = CreateCompilationWithMscorlib461(text);
            compilation.VerifyDiagnostics(
                // (6,27): error CS8081: Expression does not have a name.
                //         string s = nameof((System.Action)(() => M(M(out var z1), z1))).ToString();
                Diagnostic(ErrorCode.ERR_ExpressionHasNoName, "(System.Action)(() => M(M(out var z1), z1))").WithLocation(6, 27),
                // (7,18): error CS0103: The name 'z1' does not exist in the current context
                //         bool c = z1 == 0;
                Diagnostic(ErrorCode.ERR_NameNotInContext, "z1").WithArguments("z1").WithLocation(7, 18)
                );
            var tree = compilation.SyntaxTrees[0];
            var model = compilation.GetSemanticModel(tree);

            var name = "z1";
            var decl = GetOutVarDeclaration(tree, name);
            var refs = GetReferences(tree, name).ToArray();
            Assert.Equal(2, refs.Length);
            VerifyModelForOutVar(model, decl, isDelegateCreation: false, isExecutableCode: false, isShadowed: false, references: refs[0]);
            VerifyNotInScope(model, refs[1]);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("System.Int32", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_01()
        {
            string source = @"
class C
{
    void M<T>()
    {
        void Local1 (Action<T> onNext = p =>
                                        {
                                            weakRef.TryGetTarget(out var x);
                                        })
        {
        }
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType)); // crashes

            var decl = GetOutVarDeclaration(tree, "x");
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_02()
        {
            string source = @"
class C
{
    void M<T>()
    {
        void Local1 (Action<T> onNext = p1 =>
                                        {
                                            void Local1 (Action<T> onNext = p2 =>
                                                                            {
                                                                                weakRef.TryGetTarget(out var x);
                                                                            })
                                            {
                                            }
                                        })
        {
        }
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType)); // crashes

            var decl = GetOutVarDeclaration(tree, "x");
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_03()
        {
            string source = @"
class C
{
    void M<T>()
    {
        void Local1 (Action<T> onNext = p1 =>
                                        {
                                            void Local1 (Action<T> onNext = p2 =>
                                                                            {
                                                                                void Local1 (Action<T> onNext = p3 =>
                                                                                                                {
                                                                                                                    weakRef.TryGetTarget(out var x);
                                                                                                                })
                                                                                {
                                                                                }
                                                                            })
                                            {
                                            }
                                        })
        {
        }
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType)); // crashes

            var decl = GetOutVarDeclaration(tree, "x");
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_04()
        {
            string source = @"
class C
{
    void M<T>()
    {
        void Local1 (object onNext = from p in y select weakRef.TryGetTarget(out var x))
        {
        }
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType)); // crashes

            var decl = GetOutVarDeclaration(tree, "x");
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_05()
        {
            string source = @"
class C
{
    void M<T>()
    {
        void Local1 (object onNext = from p in y 
                                     select (Action<T>)( p =>
                                                        {
                                                            void Local2 (object onNext = from p in y select weakRef.TryGetTarget(out var x))
                                                            {
                                                            }
                                                        }
                                                        )
                    )
        {
        }
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType)); // crashes

            var decl = GetOutVarDeclaration(tree, "x");
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_06()
        {
            string source = @"
class C
{
    void M<T>()
    {
        System.Type t = typeof(int[p =>
                                    {
                                        weakRef.TryGetTarget(out var x);
                                    }]);
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType));

            var decl = GetOutVarDeclaration(tree, "x");
            Assert.Equal("var", model.GetTypeInfo(decl).Type.ToTestDisplayString()); // crashes
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_07()
        {
            string source = @"
class C
{
    void M<T>()
    {
        System.Type t1 = typeof(int[p1 =>
                                    {
                                        System.Type t2 = typeof(int[p2 =>
                                                                    {
                                                                        weakRef.TryGetTarget(out var x);
                                                                    }]);
                                    }]);
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType));

            var decl = GetOutVarDeclaration(tree, "x");
            Assert.Equal("var", model.GetTypeInfo(decl).Type.ToTestDisplayString()); // crashes
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_08()
        {
            string source = @"
class C
{
    void M<T>()
    {
        System.Type t1 = typeof(int[p1 =>
                                    {
                                        System.Type t2 = typeof(int[p2 =>
                                                                    {
                                                                        System.Type t3 = typeof(int[p3 =>
                                                                                                    {
                                                                                                        weakRef.TryGetTarget(out var x);
                                                                                                    }]);
                                                                    }]);
                                    }]);
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType));

            var decl = GetOutVarDeclaration(tree, "x");
            Assert.Equal("var", model.GetTypeInfo(decl).Type.ToTestDisplayString()); // crashes
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_09()
        {
            string source = @"
class C
{
    void M<T>()
    {
        System.Type t = typeof(int[from p in y select weakRef.TryGetTarget(out var x)]);
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType));

            var decl = GetOutVarDeclaration(tree, "x");
            Assert.Equal("var", model.GetTypeInfo(decl).Type.ToTestDisplayString()); // crashes
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(16919, "https://github.com/dotnet/roslyn/issues/16919")]
        [WorkItem(378641, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=378641")]
        public void GetEnclosingBinderInternalRecovery_10()
        {
            string source = @"
class C
{
    void M<T>()
    {
        System.Type t1 = typeof(int[from p in y 
                                    select (Action<T>)( p =>
                                                        {
                                                            System.Type t2 = typeof(int[from p in y select weakRef.TryGetTarget(out var x)]);
                                                        }
                                                        )
                                   ]
                               );
    }
}
";
            var compilation = CreateCompilation(source);

            var tree = compilation.SyntaxTrees.First();
            var model = compilation.GetSemanticModel(tree);

            var varType = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "var").Single();
            Assert.Equal("var", varType.ToString());
            Assert.Null(model.GetAliasInfo(varType));

            var decl = GetOutVarDeclaration(tree, "x");
            Assert.Equal("var", model.GetTypeInfo(decl).Type.ToTestDisplayString()); // crashes
            VerifyModelForOutVarInNotExecutableCode(model, decl);
            var symbol = (ILocalSymbol)model.GetDeclaredSymbol(decl.Designation);
            Assert.Equal("var", symbol.Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(445600, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=445600")]
        public void GetEnclosingBinderInternalRecovery_11()
        {
            var text = @"
class Program
{
    static void Main(string[] args)
    {
        foreach 
        other(some().F(a => TestOutVar(out var x) ? x : 1));
    }

    static void TestOutVar(out int a)
    {
        a = 0;
    }
}
";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe);
            compilation.VerifyDiagnostics(
                // (6,16): error CS1003: Syntax error, '(' expected
                //         foreach 
                Diagnostic(ErrorCode.ERR_SyntaxError, "").WithArguments("(").WithLocation(6, 16),
                // (7,60): error CS1515: 'in' expected
                //         other(some().F(a => TestOutVar(out var x) ? x : 1));
                Diagnostic(ErrorCode.ERR_InExpected, ";").WithLocation(7, 60),
                // (7,60): error CS0230: Type and identifier are both required in a foreach statement
                //         other(some().F(a => TestOutVar(out var x) ? x : 1));
                Diagnostic(ErrorCode.ERR_BadForeachDecl, ";").WithLocation(7, 60),
                // (7,60): error CS1525: Invalid expression term ';'
                //         other(some().F(a => TestOutVar(out var x) ? x : 1));
                Diagnostic(ErrorCode.ERR_InvalidExprTerm, ";").WithArguments(";").WithLocation(7, 60),
                // (7,60): error CS1026: ) expected
                //         other(some().F(a => TestOutVar(out var x) ? x : 1));
                Diagnostic(ErrorCode.ERR_CloseParenExpected, ";").WithLocation(7, 60)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var xDecl = GetOutVarDeclaration(tree, "x");
            var xRef = GetReferences(tree, "x", 1);
            VerifyModelForOutVarWithoutDataFlow(model, xDecl, xRef);
            Assert.Equal("System.Int32", compilation.GetSemanticModel(tree).GetTypeInfo(xRef[0]).Type.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(17208, "https://github.com/dotnet/roslyn/issues/17208")]
        public void ErrorRecoveryShouldIgnoreNonDelegates()
        {
            var source =
@"using System;
class C
{
    static void Main()
    {
        G(x => x > 0 && F(out var y) && y > 0);
    }
    static bool F(out int i)
    {
        i = 0;
        return true;
    }
    static void G(Func<int, bool> f, object o) { }
    static void G(C c, object o) { }
}";
            var comp = CreateCompilationWithMscorlib40AndSystemCore(source);
            comp.VerifyDiagnostics(
                // (6,9): error CS1501: No overload for method 'G' takes 1 arguments
                //         G(x => x > 0 && F(out var y) && y > 0);
                Diagnostic(ErrorCode.ERR_BadArgCount, "G").WithArguments("G", "1").WithLocation(6, 9));
        }

        [Fact]
        [WorkItem(17208, "https://github.com/dotnet/roslyn/issues/17208")]
        public void ErrorRecoveryShouldIgnoreNonDelegates_Expression()
        {
            var source =
@"using System;
using System.Linq.Expressions;
class C
{
    static void Main()
    {
        G(x => x > 0 && F(out var y) && y > 0);
    }
    static bool F(out int i)
    {
        i = 0;
        return true;
    }
    static void G(Expression<Func<int, bool>> f, object o) { }
    static void G(C c, object o) { }
}";
            var comp = CreateCompilationWithMscorlib40AndSystemCore(source);
            comp.VerifyDiagnostics(
                // (7,9): error CS1501: No overload for method 'G' takes 1 arguments
                //         G(x => x > 0 && F(out var y) && y > 0);
                Diagnostic(ErrorCode.ERR_BadArgCount, "G").WithArguments("G", "1").WithLocation(7, 9));
        }

        [Fact]
        [WorkItem(17208, "https://github.com/dotnet/roslyn/issues/17208")]
        public void ErrorRecoveryShouldIgnoreNonDelegates_Query()
        {
            var source =
@"using System.Linq;
class C
{
    static void M()
    {
        var c = from x in new[] { 1, 2, 3 }
            group x > 1 && F(out var y) && y == null
            by x;
    }
    static bool F(out object o)
    {
        o = null;
        return true;
    }
}";
            var comp = CreateCompilationWithMscorlib40AndSystemCore(source);
            comp.VerifyDiagnostics();
        }

        [Fact]
        [WorkItem(388744, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=388744")]
        public void SpeculativeSemanticModelWithOutDiscard()
        {
            var source =
@"class C
{
    static void F()
    {
        C.G(out _);
    }
    static void G(out object o)
    {
        o = null;
    }
}";
            var comp = CreateCompilation(source);
            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);
            var identifierBefore = GetReferences(tree, "G").Single();
            Assert.Equal(tree, identifierBefore.Location.SourceTree);
            var statementBefore = identifierBefore.Ancestors().OfType<StatementSyntax>().First();
            var statementAfter = SyntaxFactory.ParseStatement(@"G(out _);");
            bool success = model.TryGetSpeculativeSemanticModel(statementBefore.SpanStart, statementAfter, out model);
            Assert.True(success);
            var identifierAfter = statementAfter.DescendantNodes().OfType<IdentifierNameSyntax>().Single(id => id.Identifier.ValueText == "G");
            Assert.Null(identifierAfter.Location.SourceTree);
            var info = model.GetSymbolInfo(identifierAfter);
            Assert.Equal("void C.G(out System.Object o)", info.Symbol.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(10604, "https://github.com/dotnet/roslyn/issues/10604")]
        [WorkItem(16306, "https://github.com/dotnet/roslyn/issues/16306")]
        public void GetForEachSymbolInfoWithOutVar()
        {
            var source =
@"using System.Collections.Generic;
public class C
{
    void M()
    {
        foreach (var x in M2(out int i)) { }
    }
    IEnumerable<object> M2(out int j)
    {
        throw null;
    }
}";
            var comp = CreateCompilation(source, options: TestOptions.DebugDll);
            comp.VerifyDiagnostics();

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);
            var foreachStatement = tree.GetRoot().DescendantNodes().OfType<ForEachStatementSyntax>().Single();
            var info = model.GetForEachStatementInfo(foreachStatement);
            Assert.Equal("System.Object", info.ElementType.ToTestDisplayString());
            Assert.Equal("System.Collections.Generic.IEnumerator<System.Object> System.Collections.Generic.IEnumerable<System.Object>.GetEnumerator()",
                info.GetEnumeratorMethod.ToTestDisplayString());
        }

        [WorkItem(19382, "https://github.com/dotnet/roslyn/issues/19382")]
        [ConditionalFact(typeof(DesktopOnly), Reason = ConditionalSkipReason.RestrictedTypesNeedDesktop)]
        public void DiscardAndArgList()
        {
            var text = @"
using System;
public class C
{
    static void Main()
    {
        M(out _, __arglist(2, 3, true));
    }
    
    static void M(out int x, __arglist)
    {    
        x = 0;
        DumpArgs(new ArgIterator(__arglist));
    }

    static void DumpArgs(ArgIterator args)
    {
        while(args.GetRemainingCount() > 0)
        {
            TypedReference tr = args.GetNextArg();
            object arg = TypedReference.ToObject(tr);
            Console.Write(arg);
        }
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics();

            CompileAndVerify(compilation, expectedOutput: "23True");
        }

        [Fact]
        [WorkItem(23378, "https://github.com/dotnet/roslyn/issues/23378")]
        public void OutVarInArgList_01()
        {
            var text = @"
public class C
{
    static void Main()
    {
        M(1, __arglist(out int y));
        M(2, __arglist(out var z));
        System.Console.WriteLine(z);
    }
    
    static void M(int x, __arglist)
    {    
        x = 0;
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,28): error CS8378: __arglist cannot have an argument passed by 'in' or 'out'
                //         M(1, __arglist(out int y));
                Diagnostic(ErrorCode.ERR_CantUseInOrOutInArglist, "int y").WithLocation(6, 28),
                // (7,32): error CS8197: Cannot infer the type of implicitly-typed out variable 'z'.
                //         M(2, __arglist(out var z));
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "z").WithArguments("z").WithLocation(7, 32),
                // (7,28): error CS8378: __arglist cannot have an argument passed by 'in' or 'out'
                //         M(2, __arglist(out var z));
                Diagnostic(ErrorCode.ERR_CantUseInOrOutInArglist, "var z").WithLocation(7, 28)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var zDecl = GetOutVarDeclaration(tree, "z");
            var zRef = GetReference(tree, "z");
            VerifyModelForOutVar(model, zDecl, zRef);
        }

        [Fact]
        [WorkItem(23378, "https://github.com/dotnet/roslyn/issues/23378")]
        public void OutVarInArgList_02()
        {
            var text = @"
public class C
{
    static void Main()
    {
        __arglist(out int y);
        __arglist(out var z);
        System.Console.WriteLine(z);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,23): error CS8378: __arglist cannot have an argument passed by 'in' or 'out'
                //         __arglist(out int y);
                Diagnostic(ErrorCode.ERR_CantUseInOrOutInArglist, "int y").WithLocation(6, 23),
                // (6,9): error CS0226: An __arglist expression may only appear inside of a call or new expression
                //         __arglist(out int y);
                Diagnostic(ErrorCode.ERR_IllegalArglist, "__arglist(out int y)").WithLocation(6, 9),
                // (7,27): error CS8197: Cannot infer the type of implicitly-typed out variable 'z'.
                //         __arglist(out var z);
                Diagnostic(ErrorCode.ERR_TypeInferenceFailedForImplicitlyTypedOutVariable, "z").WithArguments("z").WithLocation(7, 27),
                // (7,23): error CS8378: __arglist cannot have an argument passed by 'in' or 'out'
                //         __arglist(out var z);
                Diagnostic(ErrorCode.ERR_CantUseInOrOutInArglist, "var z").WithLocation(7, 23),
                // (7,9): error CS0226: An __arglist expression may only appear inside of a call or new expression
                //         __arglist(out var z);
                Diagnostic(ErrorCode.ERR_IllegalArglist, "__arglist(out var z)").WithLocation(7, 9)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var zDecl = GetOutVarDeclaration(tree, "z");
            var zRef = GetReference(tree, "z");
            VerifyModelForOutVar(model, zDecl, zRef);
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void OutVarInNewT_01()
        {
            var text = @"
public class C
{
    static void M<T>() where T : new()
    {
        var x = new T(out var z);
        System.Console.WriteLine(z);
    }
}";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,17): error CS0417: 'T': cannot provide arguments when creating an instance of a variable type
                //         var x = new T(out var z);
                Diagnostic(ErrorCode.ERR_NewTyvarWithArgs, "new T(out var z)").WithArguments("T").WithLocation(6, 17)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var zDecl = GetOutVarDeclaration(tree, "z");
            var zRef = GetReference(tree, "z");
            VerifyModelForOutVarWithoutDataFlow(model, zDecl, zRef);

            var node = tree.GetRoot().DescendantNodes().OfType<ObjectCreationExpressionSyntax>().Single();

            Assert.Equal("new T(out var z)", node.ToString());

            compilation.VerifyOperationTree(node, expectedOperationTree:
@"
IInvalidOperation (OperationKind.Invalid, Type: T, IsInvalid) (Syntax: 'new T(out var z)')
  Children(1):
      IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: var, IsInvalid) (Syntax: 'var z')
        ILocalReferenceOperation: z (IsDeclaration: True) (OperationKind.LocalReference, Type: var, IsInvalid) (Syntax: 'z')
");
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void OutVarInNewT_02()
        {
            var text = @"
public class C
{
    static void M<T>() where T : C, new()
    {
        var x = new T(out var z) {F1 = 1};
        System.Console.WriteLine(z);
    }

    public int F1;
}


";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular);

            compilation.VerifyDiagnostics(
                // (6,17): error CS0417: 'T': cannot provide arguments when creating an instance of a variable type
                //         var x = new T(out var z) {F1 = 1};
                Diagnostic(ErrorCode.ERR_NewTyvarWithArgs, "new T(out var z) {F1 = 1}").WithArguments("T").WithLocation(6, 17)
                );

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var zDecl = GetOutVarDeclaration(tree, "z");
            var zRef = GetReference(tree, "z");
            VerifyModelForOutVarWithoutDataFlow(model, zDecl, zRef);

            var node = tree.GetRoot().DescendantNodes().OfType<ObjectCreationExpressionSyntax>().Single();

            Assert.Equal("new T(out var z) {F1 = 1}", node.ToString());

            compilation.VerifyOperationTree(node, expectedOperationTree:
@"
IInvalidOperation (OperationKind.Invalid, Type: T, IsInvalid) (Syntax: 'new T(out v ... z) {F1 = 1}')
  Children(2):
      IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: var, IsInvalid) (Syntax: 'var z')
        ILocalReferenceOperation: z (IsDeclaration: True) (OperationKind.LocalReference, Type: var, IsInvalid) (Syntax: 'z')
      IObjectOrCollectionInitializerOperation (OperationKind.ObjectOrCollectionInitializer, Type: T, IsInvalid) (Syntax: '{F1 = 1}')
        Initializers(1):
            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32, IsInvalid) (Syntax: 'F1 = 1')
              Left: 
                IFieldReferenceOperation: System.Int32 C.F1 (OperationKind.FieldReference, Type: System.Int32, IsInvalid) (Syntax: 'F1')
                  Instance Receiver: 
                    IInstanceReferenceOperation (ReferenceKind: ImplicitReceiver) (OperationKind.InstanceReference, Type: T, IsInvalid, IsImplicit) (Syntax: 'F1')
              Right: 
                ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 1, IsInvalid) (Syntax: '1')
");
        }

        [Fact]
        public void EventInitializers_01()
        {
            var source =
@"
public class X
{
    public static void Main()
    {
        System.Console.WriteLine(Test1());
    }

    static event System.Func<bool> Test1 = GetDelegate(TakeOutParam(1, out int x1) && Dummy(x1)); 

    static System.Func<bool> GetDelegate(bool value) => () => value;

    static bool Dummy(int x) 
    {
        System.Console.WriteLine(x);
        return true;
    }

    static bool TakeOutParam(int y, out int x) 
    {
        x = y;
        return true;
    }
}
";
            var compilation = CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
            CompileAndVerify(compilation, expectedOutput: @"1
True");

            CreateCompilationWithMscorlib461(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular7_2).VerifyDiagnostics(
                // (9,76): error CS8320: Feature 'declaration of expression variables in member initializers and queries' is not available in C# 7.2. Please use language version 7.3 or greater.
                //     static event System.Func<bool> Test1 = GetDelegate(TakeOutParam(1, out int x1) && Dummy(x1)); 
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion7_2, "int x1").WithArguments("declaration of expression variables in member initializers and queries", "7.3").WithLocation(9, 76)
                );
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void ConstructorBodyOperation()
        {
            var text = @"
public class C
{
    C() : this(out var x)
    { M(out var y); }
    => M(out var z);

    C (out int x){x=1;}
    void M (out int x){x=1;}
}


";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var initializerSyntax = tree.GetRoot().DescendantNodes().OfType<ConstructorInitializerSyntax>().Single();

            Assert.Equal(": this(out var x)", initializerSyntax.ToString());

            compilation.VerifyOperationTree(initializerSyntax, expectedOperationTree:
@"
IInvocationOperation ( C..ctor(out System.Int32 x)) (OperationKind.Invocation, Type: System.Void, IsInvalid) (Syntax: ': this(out var x)')
  Instance Receiver: 
    IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: ': this(out var x)')
  Arguments(1):
      IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var x')
        IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var x')
          ILocalReferenceOperation: x (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
            IOperation initializerOperation = model.GetOperation(initializerSyntax);
            Assert.Equal(OperationKind.ExpressionStatement, initializerOperation.Parent.Kind);

            var blockBodySyntax = tree.GetRoot().DescendantNodes().OfType<BlockSyntax>().First();

            Assert.Equal("{ M(out var y); }", blockBodySyntax.ToString());

            compilation.VerifyOperationTree(blockBodySyntax, expectedOperationTree:
@"
IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '{ M(out var y); }')
  Locals: Local_1: System.Int32 y
  IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid) (Syntax: 'M(out var y);')
    Expression: 
      IInvocationOperation ( void C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Void, IsInvalid) (Syntax: 'M(out var y)')
        Instance Receiver: 
          IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
        Arguments(1):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var y')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var y')
                ILocalReferenceOperation: y (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'y')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
            IOperation blockBodyOperation = model.GetOperation(blockBodySyntax);
            Assert.Equal(OperationKind.ConstructorBody, blockBodyOperation.Parent.Kind);
            Assert.Same(initializerOperation.Parent.Parent, blockBodyOperation.Parent);
            Assert.Null(blockBodyOperation.Parent.Parent);

            var expressionBodySyntax = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().First();

            Assert.Equal("=> M(out var z)", expressionBodySyntax.ToString());

            compilation.VerifyOperationTree(expressionBodySyntax, expectedOperationTree:
@"
IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '=> M(out var z)')
  Locals: Local_1: System.Int32 z
  IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid, IsImplicit) (Syntax: 'M(out var z)')
    Expression: 
      IInvocationOperation ( void C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Void, IsInvalid) (Syntax: 'M(out var z)')
        Instance Receiver: 
          IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
        Arguments(1):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var z')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var z')
                ILocalReferenceOperation: z (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'z')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");

            Assert.Same(blockBodyOperation.Parent, model.GetOperation(expressionBodySyntax).Parent);

            var declarationSyntax = tree.GetRoot().DescendantNodes().OfType<ConstructorDeclarationSyntax>().First();

            Assert.Same(blockBodyOperation.Parent, model.GetOperation(declarationSyntax));

            compilation.VerifyOperationTree(declarationSyntax, expectedOperationTree:
@"
IConstructorBodyOperation (OperationKind.ConstructorBody, Type: null, IsInvalid) (Syntax: 'C() : this( ... out var z);')
  Locals: Local_1: System.Int32 x
  Initializer: 
    IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid, IsImplicit) (Syntax: ': this(out var x)')
      Expression: 
        IInvocationOperation ( C..ctor(out System.Int32 x)) (OperationKind.Invocation, Type: System.Void, IsInvalid) (Syntax: ': this(out var x)')
          Instance Receiver: 
            IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: ': this(out var x)')
          Arguments(1):
              IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var x')
                IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var x')
                  ILocalReferenceOperation: x (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
                InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
  BlockBody: 
    IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '{ M(out var y); }')
      Locals: Local_1: System.Int32 y
      IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid) (Syntax: 'M(out var y);')
        Expression: 
          IInvocationOperation ( void C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Void, IsInvalid) (Syntax: 'M(out var y)')
            Instance Receiver: 
              IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
            Arguments(1):
                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var y')
                  IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var y')
                    ILocalReferenceOperation: y (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'y')
                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
  ExpressionBody: 
    IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '=> M(out var z)')
      Locals: Local_1: System.Int32 z
      IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid, IsImplicit) (Syntax: 'M(out var z)')
        Expression: 
          IInvocationOperation ( void C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Void, IsInvalid) (Syntax: 'M(out var z)')
            Instance Receiver: 
              IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
            Arguments(1):
                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var z')
                  IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var z')
                    ILocalReferenceOperation: z (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'z')
                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void MethodBodyOperation()
        {
            var text = @"
public class C
{
    int P  
    { 
        get {return M(out var x);} => M(out var y); 
    } => M(out var z);

    int M (out int x){x=1; return 1;}
}


";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var expressionBodySyntax = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().First();

            Assert.Equal("=> M(out var y)", expressionBodySyntax.ToString());

            compilation.VerifyOperationTree(expressionBodySyntax, expectedOperationTree:
@"
IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '=> M(out var y)')
  Locals: Local_1: System.Int32 y
  IReturnOperation (OperationKind.Return, Type: null, IsInvalid, IsImplicit) (Syntax: 'M(out var y)')
    ReturnedValue: 
      IInvocationOperation ( System.Int32 C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Int32, IsInvalid) (Syntax: 'M(out var y)')
        Instance Receiver: 
          IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
        Arguments(1):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var y')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var y')
                ILocalReferenceOperation: y (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'y')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
            IOperation expressionBodyOperation = model.GetOperation(expressionBodySyntax);
            Assert.Equal(OperationKind.MethodBody, expressionBodyOperation.Parent.Kind);
            Assert.Null(expressionBodyOperation.Parent.Parent);

            var blockBodySyntax = tree.GetRoot().DescendantNodes().OfType<BlockSyntax>().First();

            Assert.Equal("{return M(out var x);}", blockBodySyntax.ToString());

            compilation.VerifyOperationTree(blockBodySyntax, expectedOperationTree:
@"
IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '{return M(out var x);}')
  Locals: Local_1: System.Int32 x
  IReturnOperation (OperationKind.Return, Type: null, IsInvalid) (Syntax: 'return M(out var x);')
    ReturnedValue: 
      IInvocationOperation ( System.Int32 C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Int32, IsInvalid) (Syntax: 'M(out var x)')
        Instance Receiver: 
          IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
        Arguments(1):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var x')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var x')
                ILocalReferenceOperation: x (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");

            IOperation blockBodyOperation = model.GetOperation(blockBodySyntax);
            Assert.Same(expressionBodyOperation.Parent, blockBodyOperation.Parent);

            var propertyExpressionBodySyntax = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().ElementAt(1);

            Assert.Equal("=> M(out var z)", propertyExpressionBodySyntax.ToString());
            Assert.Null(model.GetOperation(propertyExpressionBodySyntax)); // https://github.com/dotnet/roslyn/issues/24900

            var declarationSyntax = tree.GetRoot().DescendantNodes().OfType<AccessorDeclarationSyntax>().Single();
            Assert.Same(expressionBodyOperation.Parent, model.GetOperation(declarationSyntax));
            compilation.VerifyOperationTree(declarationSyntax, expectedOperationTree:
@"
IMethodBodyOperation (OperationKind.MethodBody, Type: null, IsInvalid) (Syntax: 'get {return ... out var y);')
  BlockBody: 
    IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '{return M(out var x);}')
      Locals: Local_1: System.Int32 x
      IReturnOperation (OperationKind.Return, Type: null, IsInvalid) (Syntax: 'return M(out var x);')
        ReturnedValue: 
          IInvocationOperation ( System.Int32 C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Int32, IsInvalid) (Syntax: 'M(out var x)')
            Instance Receiver: 
              IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
            Arguments(1):
                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var x')
                  IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var x')
                    ILocalReferenceOperation: x (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
  ExpressionBody: 
    IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null, IsInvalid) (Syntax: '=> M(out var y)')
      Locals: Local_1: System.Int32 y
      IReturnOperation (OperationKind.Return, Type: null, IsInvalid, IsImplicit) (Syntax: 'M(out var y)')
        ReturnedValue: 
          IInvocationOperation ( System.Int32 C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Int32, IsInvalid) (Syntax: 'M(out var y)')
            Instance Receiver: 
              IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsInvalid, IsImplicit) (Syntax: 'M')
            Arguments(1):
                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null, IsInvalid) (Syntax: 'out var y')
                  IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32, IsInvalid) (Syntax: 'var y')
                    ILocalReferenceOperation: y (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'y')
                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
        }

        [CompilerTrait(CompilerFeature.IOperation)]
        [Fact]
        public void PropertyExpressionBodyOperation()
        {
            var text = @"
public class C
{
    int P => M(out var z);

    int M (out int x){x=1; return 1;}
}


";
            var compilation = CreateCompilation(text, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var node3 = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().First();

            Assert.Equal("=> M(out var z)", node3.ToString());

            compilation.VerifyOperationTree(node3, expectedOperationTree:
@"
IBlockOperation (1 statements, 1 locals) (OperationKind.Block, Type: null) (Syntax: '=> M(out var z)')
  Locals: Local_1: System.Int32 z
  IReturnOperation (OperationKind.Return, Type: null, IsImplicit) (Syntax: 'M(out var z)')
    ReturnedValue: 
      IInvocationOperation ( System.Int32 C.M(out System.Int32 x)) (OperationKind.Invocation, Type: System.Int32) (Syntax: 'M(out var z)')
        Instance Receiver: 
          IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsImplicit) (Syntax: 'M')
        Arguments(1):
            IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: x) (OperationKind.Argument, Type: null) (Syntax: 'out var z')
              IDeclarationExpressionOperation (OperationKind.DeclarationExpression, Type: System.Int32) (Syntax: 'var z')
                ILocalReferenceOperation: z (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'z')
              InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
              OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
");
            Assert.Null(model.GetOperation(node3).Parent);
        }

        [Fact]
        public void OutVarInConstructorUsedInObjectInitializer()
        {
            var source =
@"
public class C
{
    public int Number { get; set; }
    
    public C(out int n)
    {
        n = 1;
    }

    public static void Main()
    {
        C c = new C(out var i) { Number = i };
        System.Console.WriteLine(c.Number);
    }
}
";
            CompileAndVerify(source, expectedOutput: @"1");
        }

        [Fact]
        public void OutVarInConstructorUsedInCollectionInitializer()
        {
            var source =
@"
public class C : System.Collections.Generic.List<int>
{
    public C(out int n)
    {
        n = 1;
    }

    public static void Main()
    {
        C c = new C(out var i) { i, i, i };
        System.Console.WriteLine(c[0]);
    }
}
";
            CompileAndVerify(source, expectedOutput: @"1");
        }

        [Fact]
        [WorkItem(49997, "https://github.com/dotnet/roslyn/issues/49997")]
        public void Issue49997()
        {
            var text = @"
public class Cls
{
    public static void Main()
    {
        if ()
        .Test1().Test2(out var x1).Test3();
    }
}

static class Ext
{
    public static void Test3(this Cls x) {}
}
";
            var compilation = CreateCompilation(text);

            var tree = compilation.SyntaxTrees.Single();
            var model = compilation.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "Test3").Last();
            Assert.True(model.GetSymbolInfo(node).IsEmpty);
        }

        [Fact]
        [WorkItem(60801, "https://github.com/dotnet/roslyn/issues/60801")]
        public void GetSymbolInfoOnSpeculativeMethodBodySemanticModelInAttribute_01()
        {
            var source = @"
class C
{
    void M()
    {
        [My(M2(out var x))]
        void local(int parameter) { }
    }

    static string M2(out int x) => throw null;
}

public class MyAttribute : System.Attribute
{
    public MyAttribute(string name1) { }
}
";

            var comp = CreateCompilation(source);
            comp.VerifyDiagnostics(
                // (6,13): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
                //         [My(M2(out var x))]
                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "M2(out var x)").WithLocation(6, 13),
                // (7,14): warning CS8321: The local function 'local' is declared but never used
                //         void local(int parameter) { }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "local").WithArguments("local").WithLocation(7, 14)
                );

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var tree2 = CSharpSyntaxTree.ParseText(source);
            var method = tree2.GetRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(method.Body.SpanStart, method, out var speculativeModel));

            var invocation = tree2.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>().Single();
            Assert.Equal("M2(out var x)", invocation.ToString());
            var symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String C.M2(out System.Int32 x)", symbolInfo.Symbol.ToTestDisplayString());

            Assert.True(model.TryGetSpeculativeSemanticModel(method.Body.SpanStart + 1, method.DescendantNodes().OfType<AttributeSyntax>().Single(), out speculativeModel));
            symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String C.M2(out System.Int32 x)", symbolInfo.Symbol.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(60801, "https://github.com/dotnet/roslyn/issues/60801")]
        public void GetSymbolInfoOnSpeculativeMethodBodySemanticModelInAttribute_02()
        {
            var source = @"
class C
{
    void M()
    {
        [My(() => { [My(M2(out var x))] static string M2(out int x) => throw null; })]
        void local(int parameter) { }
    }
}

public class MyAttribute : System.Attribute
{
    public MyAttribute(string name1) { }
}
";

            var comp = CreateCompilation(source);
            comp.VerifyDiagnostics(
                // (6,41): error CS1002: ; expected
                //         [My(() => { [My(M2(out var x))] static string M2(out int x) => throw null; })]
                Diagnostic(ErrorCode.ERR_SemicolonExpected, "static").WithLocation(6, 41),
                // (7,14): warning CS8321: The local function 'local' is declared but never used
                //         void local(int parameter) { }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "local").WithArguments("local").WithLocation(7, 14));

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var tree2 = CSharpSyntaxTree.ParseText(source);
            var method = tree2.GetRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(method.Body.SpanStart, method, out var speculativeModel));

            var invocation = tree2.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>().Skip(1).First();
            Assert.Equal("M2(out var x)", invocation.ToString());
            var symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String M2(out System.Int32 x)", symbolInfo.Symbol.ToTestDisplayString());
            Assert.Same(symbolInfo.Symbol, speculativeModel.GetDeclaredSymbol(tree2.GetRoot().DescendantNodes().OfType<LocalFunctionStatementSyntax>().Where(l => l.Identifier.ValueText == "M2").Single()));
        }

        [Fact]
        [WorkItem(60801, "https://github.com/dotnet/roslyn/issues/60801")]
        public void GetSymbolInfoOnSpeculativeMethodBodySemanticModelInDefaultParameterValue_01()
        {
            var source = @"
class C
{
    void M()
    {
        void local(string parameter = M2(out var x)) { }
    }

    static string M2(out int x) => throw null;
}
";

            var comp = CreateCompilation(source);
            comp.VerifyDiagnostics(
                // (6,14): warning CS8321: The local function 'local' is declared but never used
                //         void local(string parameter = M2(out var x)) { }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "local").WithArguments("local").WithLocation(6, 14),
                // (6,39): error CS1736: Default parameter value for 'parameter' must be a compile-time constant
                //         void local(string parameter = M2(out var x)) { }
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M2(out var x)").WithArguments("parameter").WithLocation(6, 39)
                );

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var tree2 = CSharpSyntaxTree.ParseText(source);
            var method = tree2.GetRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(method.Body.SpanStart, method, out var speculativeModel));

            var invocation = tree2.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>().Single();
            Assert.Equal("M2(out var x)", invocation.ToString());
            var symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String C.M2(out System.Int32 x)", symbolInfo.Symbol.ToTestDisplayString());

            var equalsValue = method.DescendantNodes().OfType<EqualsValueClauseSyntax>().Single();
            Assert.True(model.TryGetSpeculativeSemanticModel(equalsValue.Value.SpanStart, equalsValue, out speculativeModel));
            symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String C.M2(out System.Int32 x)", symbolInfo.Symbol.ToTestDisplayString());
        }

        [Fact]
        [WorkItem(60801, "https://github.com/dotnet/roslyn/issues/60801")]
        public void GetSymbolInfoOnSpeculativeMethodBodySemanticModelInDefaultParameterValue_02()
        {
            var source = @"
class C
{
    void M()
    {
        void local(string parameter = () => { static string M2(out int x, string y = M2(out var a, ""b"")) => throw null; }) { }
    }
}
";

            var comp = CreateCompilation(source);
            comp.VerifyDiagnostics(
                // (6,14): warning CS8321: The local function 'local' is declared but never used
                //         void local(string parameter = M2(out var x)) { }
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "local").WithArguments("local").WithLocation(6, 14),
                // (6,39): error CS1736: Default parameter value for 'parameter' must be a compile-time constant
                //         void local(string parameter = () => { static string M2(out int x, string y = M2(out var a, "b")) => throw null; }) { }
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, @"() => { static string M2(out int x, string y = M2(out var a, ""b"")) => throw null; }").WithArguments("parameter").WithLocation(6, 39)
                );

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var tree2 = CSharpSyntaxTree.ParseText(source);
            var method = tree2.GetRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(method.Body.SpanStart, method, out var speculativeModel));

            var invocation = tree2.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>().Single();
            Assert.Equal(@"M2(out var a, ""b"")", invocation.ToString());
            var symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String M2(out System.Int32 x, [System.String y = null])", symbolInfo.Symbol.ToTestDisplayString());
            Assert.Same(symbolInfo.Symbol, speculativeModel.GetDeclaredSymbol(tree2.GetRoot().DescendantNodes().OfType<LocalFunctionStatementSyntax>().Where(l => l.Identifier.ValueText == "M2").Single()));
        }

        [Fact]
        public void GetSymbolInfoOnSpeculativeMethodBodySemanticModelInDefaultParameterValue_03()
        {
            var source = """
                class C
                {
                    void M()
                    {
                        var lam = (string parameter = M2(out var x)) => { };
                        _ = lam;
                    }

                    static string M2(out int x) => throw null;
                }
                """;

            var comp = CreateCompilation(source).VerifyDiagnostics(
                // (5,39): error CS1736: Default parameter value for 'parameter' must be a compile-time constant
                //         var lam = (string parameter = M2(out var x)) => { };
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, "M2(out var x)").WithArguments("parameter").WithLocation(5, 39));

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var tree2 = CSharpSyntaxTree.ParseText(source);
            var method = tree2.GetRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(method.Body.SpanStart, method, out var speculativeModel));

            var invocation = tree2.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>().Single();
            Assert.Equal("M2(out var x)", invocation.ToString());
            var symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String C.M2(out System.Int32 x)", symbolInfo.Symbol.ToTestDisplayString());

            var equalsValue = method.DescendantNodes().OfType<ParameterSyntax>().Single()
                .DescendantNodes().OfType<EqualsValueClauseSyntax>().Single();
            Assert.True(model.TryGetSpeculativeSemanticModel(equalsValue.Value.SpanStart, equalsValue, out speculativeModel));
            symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String C.M2(out System.Int32 x)", symbolInfo.Symbol.ToTestDisplayString());
        }

        [Fact]
        public void GetSymbolInfoOnSpeculativeMethodBodySemanticModelInDefaultParameterValue_04()
        {
            var source = """
                class C
                {
                    void M()
                    {
                        var lam = (string parameter = () => { static string M2(out int x, string y = M2(out var a, "b")) => throw null; }) => { };
                        _ = lam;
                    }
                }
                """;

            var comp = CreateCompilation(source).VerifyDiagnostics(
                // (5,39): error CS1736: Default parameter value for 'parameter' must be a compile-time constant
                //         var lam = (string parameter = () => { static string M2(out int x, string y = M2(out var a, "b")) => throw null; }) => { };
                Diagnostic(ErrorCode.ERR_DefaultValueMustBeConstant, @"() => { static string M2(out int x, string y = M2(out var a, ""b"")) => throw null; }").WithArguments("parameter").WithLocation(5, 39));

            var tree = comp.SyntaxTrees.Single();
            var model = comp.GetSemanticModel(tree);

            var tree2 = CSharpSyntaxTree.ParseText(source);
            var method = tree2.GetRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(method.Body.SpanStart, method, out var speculativeModel));

            var invocation = tree2.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>().Single();
            Assert.Equal(@"M2(out var a, ""b"")", invocation.ToString());
            var symbolInfo = speculativeModel.GetSymbolInfo(invocation);
            Assert.Equal("System.String M2(out System.Int32 x, [System.String y = null])", symbolInfo.Symbol.ToTestDisplayString());
            Assert.Same(symbolInfo.Symbol, speculativeModel.GetDeclaredSymbol(tree2.GetRoot().DescendantNodes().OfType<LocalFunctionStatementSyntax>().Where(l => l.Identifier.ValueText == "M2").Single()));
        }
    }

    internal static class OutVarTestsExtensions
    {
        internal static SingleVariableDesignationSyntax VariableDesignation(this DeclarationExpressionSyntax self)
        {
            return (SingleVariableDesignationSyntax)self.Designation;
        }
    }
}