src/Compilers/CSharp/Portable/Errors/MessageID.cs - main - githubmirror/roslyn

src/Compilers/CSharp/Portable/Errors/MessageID.cs
745 строк38 KB
Cyrus Najmabadi
Merge remote-tracking branch 'upstream/main' into merge-main-into-labeled-break-and-continue-2
24 июн 2026, 20:16
24 июн 2026, 20:1676234ec
// 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.

using System;
using System.Diagnostics;

namespace Microsoft.CodeAnalysis.CSharp
{
    internal enum MessageID
    {
        None = 0,
        MessageBase = 1200,

        IDS_SK_METHOD = MessageBase + 2000,
        IDS_SK_TYPE = MessageBase + 2001,
        IDS_SK_NAMESPACE = MessageBase + 2002,
        IDS_SK_FIELD = MessageBase + 2003,
        IDS_SK_PROPERTY = MessageBase + 2004,
        IDS_SK_UNKNOWN = MessageBase + 2005,
        IDS_SK_VARIABLE = MessageBase + 2006,
        IDS_SK_EVENT = MessageBase + 2007,
        IDS_SK_TYVAR = MessageBase + 2008,
        //IDS_SK_GCLASS = MessageBase + 2009,
        IDS_SK_ALIAS = MessageBase + 2010,
        //IDS_SK_EXTERNALIAS = MessageBase + 2011,
        IDS_SK_LABEL = MessageBase + 2012,
        IDS_SK_CONSTRUCTOR = MessageBase + 2013,

        IDS_NULL = MessageBase + 10001,
        //IDS_RELATEDERROR = MessageBase + 10002,
        //IDS_RELATEDWARNING = MessageBase + 10003,
        IDS_XMLIGNORED = MessageBase + 10004,
        IDS_XMLIGNORED2 = MessageBase + 10005,
        IDS_XMLFAILEDINCLUDE = MessageBase + 10006,
        IDS_XMLBADINCLUDE = MessageBase + 10007,
        IDS_XMLNOINCLUDE = MessageBase + 10008,
        IDS_XMLMISSINGINCLUDEFILE = MessageBase + 10009,
        IDS_XMLMISSINGINCLUDEPATH = MessageBase + 10010,
        IDS_GlobalNamespace = MessageBase + 10011,
        IDS_FeatureGenerics = MessageBase + 12500,
        IDS_FeatureAnonDelegates = MessageBase + 12501,
        IDS_FeatureModuleAttrLoc = MessageBase + 12502,
        IDS_FeatureGlobalNamespace = MessageBase + 12503,
        IDS_FeatureFixedBuffer = MessageBase + 12504,
        IDS_FeaturePragma = MessageBase + 12505,
        IDS_FOREACHLOCAL = MessageBase + 12506,
        IDS_USINGLOCAL = MessageBase + 12507,
        IDS_FIXEDLOCAL = MessageBase + 12508,
        IDS_FeatureStaticClasses = MessageBase + 12511,
        IDS_FeaturePartialTypes = MessageBase + 12512,
        IDS_MethodGroup = MessageBase + 12513,
        IDS_AnonMethod = MessageBase + 12514,
        IDS_FeatureSwitchOnBool = MessageBase + 12517,
        //IDS_WarnAsError = MessageBase + 12518,
        IDS_Collection = MessageBase + 12520,
        IDS_FeaturePropertyAccessorMods = MessageBase + 12522,
        IDS_FeatureExternAlias = MessageBase + 12523,
        IDS_FeatureIterators = MessageBase + 12524,
        IDS_FeatureDefault = MessageBase + 12525,
        IDS_FeatureNullable = MessageBase + 12528,
        IDS_Lambda = MessageBase + 12531,
        IDS_FeaturePatternMatching = MessageBase + 12532,
        IDS_FeatureThrowExpression = MessageBase + 12533,

        IDS_FeatureImplicitArray = MessageBase + 12557,
        IDS_FeatureImplicitLocal = MessageBase + 12558,
        IDS_FeatureAnonymousTypes = MessageBase + 12559,
        IDS_FeatureAutoImplementedProperties = MessageBase + 12560,
        IDS_FeatureObjectInitializer = MessageBase + 12561,
        IDS_FeatureCollectionInitializer = MessageBase + 12562,
        IDS_FeatureLambda = MessageBase + 12563,
        IDS_FeatureQueryExpression = MessageBase + 12564,
        IDS_FeatureExtensionMethod = MessageBase + 12565,
        IDS_FeaturePartialMethod = MessageBase + 12566,
        IDS_FeatureDynamic = MessageBase + 12644,
        IDS_FeatureTypeVariance = MessageBase + 12645,
        IDS_FeatureNamedArgument = MessageBase + 12646,
        IDS_FeatureOptionalParameter = MessageBase + 12647,
        IDS_FeatureExceptionFilter = MessageBase + 12648,
        IDS_FeatureAutoPropertyInitializer = MessageBase + 12649,

        IDS_SK_TYPE_OR_NAMESPACE = MessageBase + 12652,
        IDS_SK_ARRAY = MessageBase + 12653,
        IDS_SK_POINTER = MessageBase + 12654,
        IDS_SK_FUNCTION_POINTER = MessageBase + 12655,
        IDS_SK_DYNAMIC = MessageBase + 12656,

        IDS_Contravariant = MessageBase + 12659,
        IDS_Contravariantly = MessageBase + 12660,
        IDS_Covariant = MessageBase + 12661,
        IDS_Covariantly = MessageBase + 12662,
        IDS_Invariantly = MessageBase + 12663,

        IDS_FeatureAsync = MessageBase + 12668,
        IDS_FeatureStaticAnonymousFunction = MessageBase + 12669,

        IDS_LIB_ENV = MessageBase + 12680,
        IDS_LIB_OPTION = MessageBase + 12681,
        IDS_REFERENCEPATH_OPTION = MessageBase + 12682,
        IDS_DirectoryDoesNotExist = MessageBase + 12683,
        IDS_DirectoryHasInvalidPath = MessageBase + 12684,

        IDS_Namespace1 = MessageBase + 12685,
        IDS_PathList = MessageBase + 12686,
        IDS_Text = MessageBase + 12687,

        IDS_FeatureDiscards = MessageBase + 12688,

        IDS_FeatureDefaultTypeParameterConstraint = MessageBase + 12689,
        IDS_FeatureNullPropagatingOperator = MessageBase + 12690,
        IDS_FeatureExpressionBodiedMethod = MessageBase + 12691,
        IDS_FeatureExpressionBodiedProperty = MessageBase + 12692,
        IDS_FeatureExpressionBodiedIndexer = MessageBase + 12693,
        // IDS_VersionExperimental = MessageBase + 12694,
        IDS_FeatureNameof = MessageBase + 12695,
        IDS_FeatureDictionaryInitializer = MessageBase + 12696,

        IDS_ToolName = MessageBase + 12697,
        IDS_LogoLine1 = MessageBase + 12698,
        IDS_LogoLine2 = MessageBase + 12699,
        IDS_CSCHelp = MessageBase + 12700,

        IDS_FeatureUsingStatic = MessageBase + 12701,
        IDS_FeatureInterpolatedStrings = MessageBase + 12702,
        IDS_OperationCausedStackOverflow = MessageBase + 12703,
        IDS_AwaitInCatchAndFinally = MessageBase + 12704,
        IDS_FeatureReadonlyAutoImplementedProperties = MessageBase + 12705,
        IDS_FeatureBinaryLiteral = MessageBase + 12706,
        IDS_FeatureDigitSeparator = MessageBase + 12707,
        IDS_FeatureLocalFunctions = MessageBase + 12708,
        IDS_FeatureNullableReferenceTypes = MessageBase + 12709,

        IDS_FeatureRefLocalsReturns = MessageBase + 12710,
        IDS_FeatureTuples = MessageBase + 12711,
        IDS_FeatureOutVar = MessageBase + 12713,

        // IDS_FeaturePragmaWarningEnable = MessageBase + 12714,
        IDS_FeatureExpressionBodiedAccessor = MessageBase + 12715,
        IDS_FeatureExpressionBodiedDeOrConstructor = MessageBase + 12716,
        IDS_ThrowExpression = MessageBase + 12717,
        IDS_FeatureDefaultLiteral = MessageBase + 12718,
        IDS_FeatureInferredTupleNames = MessageBase + 12719,
        IDS_FeatureGenericPatternMatching = MessageBase + 12720,
        IDS_FeatureAsyncMain = MessageBase + 12721,
        IDS_LangVersions = MessageBase + 12722,

        IDS_FeatureLeadingDigitSeparator = MessageBase + 12723,
        IDS_FeatureNonTrailingNamedArguments = MessageBase + 12724,

        IDS_FeatureReadOnlyReferences = MessageBase + 12725,
        IDS_FeatureRefStructs = MessageBase + 12726,
        IDS_FeatureReadOnlyStructs = MessageBase + 12727,
        IDS_FeatureRefExtensionMethods = MessageBase + 12728,
        // IDS_StackAllocExpression = MessageBase + 12729,
        IDS_FeaturePrivateProtected = MessageBase + 12730,

        IDS_FeatureRefConditional = MessageBase + 12731,
        IDS_FeatureAttributesOnBackingFields = MessageBase + 12732,
        IDS_FeatureImprovedOverloadCandidates = MessageBase + 12733,
        IDS_FeatureRefReassignment = MessageBase + 12734,
        IDS_FeatureRefFor = MessageBase + 12735,
        IDS_FeatureRefForEach = MessageBase + 12736,
        IDS_FeatureEnumGenericTypeConstraint = MessageBase + 12737,
        IDS_FeatureDelegateGenericTypeConstraint = MessageBase + 12738,
        IDS_FeatureUnmanagedGenericTypeConstraint = MessageBase + 12739,
        IDS_FeatureStackAllocInitializer = MessageBase + 12740,
        IDS_FeatureTupleEquality = MessageBase + 12741,
        IDS_FeatureExpressionVariablesInQueriesAndInitializers = MessageBase + 12742,
        IDS_FeatureExtensibleFixedStatement = MessageBase + 12743,
        IDS_FeatureIndexingMovableFixedBuffers = MessageBase + 12744,

        IDS_FeatureAltInterpolatedVerbatimStrings = MessageBase + 12745,
        IDS_FeatureCoalesceAssignmentExpression = MessageBase + 12746,
        IDS_FeatureUnconstrainedTypeParameterInNullCoalescingOperator = MessageBase + 12747,
        IDS_FeatureNotNullGenericTypeConstraint = MessageBase + 12748,
        IDS_FeatureIndexOperator = MessageBase + 12749,
        IDS_FeatureRangeOperator = MessageBase + 12750,
        IDS_FeatureAsyncStreams = MessageBase + 12751,
        IDS_FeatureRecursivePatterns = MessageBase + 12752,
        IDS_Disposable = MessageBase + 12753,
        IDS_FeatureUsingDeclarations = MessageBase + 12754,
        IDS_FeatureStaticLocalFunctions = MessageBase + 12755,
        IDS_FeatureNameShadowingInNestedFunctions = MessageBase + 12756,
        IDS_FeatureUnmanagedConstructedTypes = MessageBase + 12757,
        IDS_FeatureObsoleteOnPropertyAccessor = MessageBase + 12758,
        IDS_FeatureReadOnlyMembers = MessageBase + 12759,
        IDS_DefaultInterfaceImplementation = MessageBase + 12760,
        IDS_OverrideWithConstraints = MessageBase + 12761,
        IDS_FeatureNestedStackalloc = MessageBase + 12762,
        IDS_FeatureSwitchExpression = MessageBase + 12763,
        IDS_FeatureAsyncUsing = MessageBase + 12764,
        IDS_FeatureLambdaDiscardParameters = MessageBase + 12765,
        IDS_FeatureLocalFunctionAttributes = MessageBase + 12766,
        IDS_FeatureExternLocalFunctions = MessageBase + 12767,
        IDS_FeatureMemberNotNull = MessageBase + 12768,

        IDS_FeatureNativeInt = MessageBase + 12769,
        IDS_FeatureImplicitObjectCreation = MessageBase + 12770,
        IDS_FeatureTypePattern = MessageBase + 12771,
        IDS_FeatureParenthesizedPattern = MessageBase + 12772,
        IDS_FeatureOrPattern = MessageBase + 12773,
        IDS_FeatureAndPattern = MessageBase + 12774,
        IDS_FeatureNotPattern = MessageBase + 12775,
        IDS_FeatureRelationalPattern = MessageBase + 12776,
        IDS_FeatureExtendedPartialMethods = MessageBase + 12777,
        IDS_TopLevelStatements = MessageBase + 12778,
        IDS_FeatureFunctionPointers = MessageBase + 12779,
        IDS_AddressOfMethodGroup = MessageBase + 12780,
        IDS_FeatureInitOnlySetters = MessageBase + 12781,
        IDS_FeatureRecords = MessageBase + 12782,
        IDS_FeatureNullPointerConstantPattern = MessageBase + 12783,
        IDS_FeatureModuleInitializers = MessageBase + 12784,
        IDS_FeatureTargetTypedConditional = MessageBase + 12785,
        IDS_FeatureCovariantReturnsForOverrides = MessageBase + 12786,
        IDS_FeatureExtensionGetEnumerator = MessageBase + 12787,
        IDS_FeatureExtensionGetAsyncEnumerator = MessageBase + 12788,
        IDS_Parameter = MessageBase + 12789,
        IDS_Return = MessageBase + 12790,
        IDS_FeatureVarianceSafetyForStaticInterfaceMembers = MessageBase + 12791,
        IDS_FeatureConstantInterpolatedStrings = MessageBase + 12792,
        IDS_FeatureMixedDeclarationsAndExpressionsInDeconstruction = MessageBase + 12793,
        IDS_FeatureSealedToStringInRecord = MessageBase + 12794,
        IDS_FeatureRecordStructs = MessageBase + 12795,
        IDS_FeatureWithOnStructs = MessageBase + 12796,
        IDS_FeaturePositionalFieldsInRecords = MessageBase + 12797,
        IDS_FeatureGlobalUsing = MessageBase + 12798,
        IDS_FeatureInferredDelegateType = MessageBase + 12799,
        IDS_FeatureLambdaAttributes = MessageBase + 12800,

        IDS_FeatureWithOnAnonymousTypes = MessageBase + 12801,
        IDS_FeatureExtendedPropertyPatterns = MessageBase + 12802,
        IDS_FeatureStaticAbstractMembersInInterfaces = MessageBase + 12803,
        IDS_FeatureLambdaReturnType = MessageBase + 12804,
        IDS_AsyncMethodBuilderOverride = MessageBase + 12805,
        IDS_FeatureImplicitImplementationOfNonPublicMembers = MessageBase + 12806,
        // IDS_FeatureLineSpanDirective = MessageBase + 12807, // feature no longer gated on LangVer
        IDS_FeatureImprovedInterpolatedStrings = MessageBase + 12808,
        IDS_FeatureFileScopedNamespace = MessageBase + 12809,
        IDS_FeatureParameterlessStructConstructors = MessageBase + 12810,
        IDS_FeatureStructFieldInitializers = MessageBase + 12811,

        IDS_FeatureGenericAttributes = MessageBase + 12812,

        IDS_FeatureNewLinesInInterpolations = MessageBase + 12813,
        IDS_FeatureListPattern = MessageBase + 12814,
        // IDS_ParameterNullChecking = MessageBase + 12815, // feature removed from C# 11

        IDS_FeatureCacheStaticMethodGroupConversion = MessageBase + 12816,
        IDS_FeatureRawStringLiterals = MessageBase + 12817,
        IDS_FeatureSpanCharConstantPattern = MessageBase + 12818,
        IDS_FeatureDisposalPattern = MessageBase + 12819,
        IDS_FeatureAutoDefaultStructs = MessageBase + 12820,

        IDS_FeatureCheckedUserDefinedOperators = MessageBase + 12821,
        IDS_FeatureUtf8StringLiterals = MessageBase + 12822,

        IDS_FeatureUnsignedRightShift = MessageBase + 12823,

        IDS_FeatureRelaxedShiftOperator = MessageBase + 12824,
        IDS_FeatureRequiredMembers = MessageBase + 12825,
        IDS_FeatureRefFields = MessageBase + 12826,
        IDS_FeatureFileTypes = MessageBase + 12827,
        IDS_ArrayAccess = MessageBase + 12828,
        IDS_PointerElementAccess = MessageBase + 12829,
        IDS_Missing = MessageBase + 12830,
        IDS_FeatureLambdaOptionalParameters = MessageBase + 12831,
        IDS_FeatureLambdaParamsArray = MessageBase + 12832,

        IDS_FeaturePrimaryConstructors = MessageBase + 12833,
        IDS_FeatureUsingTypeAlias = MessageBase + 12834,

        IDS_FeatureInstanceMemberInNameof = MessageBase + 12835,

        IDS_FeatureInlineArrays = MessageBase + 12836,
        IDS_FeatureCollectionExpressions = MessageBase + 12837,
        IDS_FeatureRefReadonlyParameters = MessageBase + 12838,
        IDS_FeatureStringEscapeCharacter = MessageBase + 12839,

        IDS_FeatureImplicitIndexerInitializer = MessageBase + 12840,
        IDS_FeatureLockObject = MessageBase + 12841,

        IDS_FeatureParamsCollections = MessageBase + 12842,

        IDS_FeatureRefUnsafeInIteratorAsync = MessageBase + 12843,

        IDS_FeatureRefStructInterfaces = MessageBase + 12844,

        IDS_FeaturePartialProperties = MessageBase + 12845,
        IDS_FeatureFieldKeyword = MessageBase + 12846,

        IDS_FeatureAllowsRefStructConstraint = MessageBase + 12847,
        IDS_FeatureOverloadResolutionPriority = MessageBase + 12848,

        IDS_FeatureFirstClassSpan = MessageBase + 12849,

        IDS_FeatureUnboundGenericTypesInNameof = MessageBase + 12850,
        IDS_FeatureSimpleLambdaParameterModifiers = MessageBase + 12851,

        IDS_FeaturePartialEventsAndConstructors = MessageBase + 12852,
        IDS_FeatureExtensions = MessageBase + 12853,
        IDS_FeatureNullConditionalAssignment = MessageBase + 12854,
        IDS_FeatureExpressionOptionalAndNamedArguments = MessageBase + 12855,
        IDS_CollectionExpression = MessageBase + 12856,

        IDS_FeatureUserDefinedCompoundAssignmentOperators = MessageBase + 12857,

        IDS_FeatureCollectionExpressionArguments = MessageBase + 12858,

        IDS_FeatureUnsafeEvolution = MessageBase + 12859,

        IDS_FeatureUnions = MessageBase + 12860,
        IDS_FeatureStaticMembersInInterfaces = MessageBase + 12861,
        IDS_FeatureClosedClasses = MessageBase + 12862,
        IDS_FeatureExtensionIndexers = MessageBase + 12863,
        IDS_FeatureLabeledBreakContinue = MessageBase + 12864,
    }

    // Message IDs may refer to strings that need to be localized.
    // This struct makes an IFormattable wrapper around a MessageID
    internal readonly struct LocalizableErrorArgument : IFormattable
    {
        private readonly MessageID _id;

        internal LocalizableErrorArgument(MessageID id)
        {
            _id = id;
        }

        public override string ToString()
        {
            return ToString(null, null);
        }

        public string ToString(string? format, IFormatProvider? formatProvider)
        {
            return ErrorFacts.GetMessage(_id, formatProvider as System.Globalization.CultureInfo);
        }
    }

    // And this extension method makes it easy to localize MessageIDs:

    internal static partial class MessageIDExtensions
    {
        public static LocalizableErrorArgument Localize(this MessageID id)
        {
            return new LocalizableErrorArgument(id);
        }

        // Returns the string to be used in the /features flag switch to enable the MessageID feature.
        // Always call this before RequiredVersion:
        //   If this method returns null, call RequiredVersion and use that.
        //   If this method returns non-null, use that.
        // Features should be mutually exclusive between RequiredFeature and RequiredVersion.
        //   (hence the above rule - RequiredVersion throws when RequiredFeature returns non-null)
        internal static string? RequiredFeature(this MessageID feature)
        {
            // Check for current experimental features, if any, in the current branch.
            switch (feature)
            {
                default:
                    return null;
            }
        }

        internal static bool CheckFeatureAvailability(
            this MessageID feature,
            DiagnosticBag diagnostics,
            SyntaxNode syntax,
            Location? location = null)
        {
            return CheckFeatureAvailability(
                feature,
                diagnostics,
                syntax.SyntaxTree.Options,
                static tuple => tuple.location ?? tuple.syntax.Location,
                (syntax, location));
        }

        internal static bool CheckFeatureAvailability(
            this MessageID feature,
            DiagnosticBag diagnostics,
            SyntaxToken syntax,
            Location? location = null)
        {
            return CheckFeatureAvailability(
                feature,
                diagnostics,
                syntax.SyntaxTree!.Options,
                static tuple => tuple.location ?? tuple.syntax.GetLocation(),
                (syntax, location));
        }

        internal static bool CheckFeatureAvailability(
            this MessageID feature,
            BindingDiagnosticBag diagnostics,
            SyntaxNode syntax,
            Location? location = null)
        {
            return CheckFeatureAvailability(
                feature,
                diagnostics,
                syntax.SyntaxTree.Options,
                static tuple => tuple.location ?? tuple.syntax.Location,
                (syntax, location));
        }

        internal static bool CheckFeatureAvailability(
            this MessageID feature,
            BindingDiagnosticBag diagnostics,
            SyntaxToken syntax,
            Location? location = null)
        {
            return CheckFeatureAvailability(
                feature,
                diagnostics,
                syntax.SyntaxTree!.Options,
                static tuple => tuple.location ?? tuple.syntax.GetLocation(),
                (syntax, location));
        }

        private static bool CheckFeatureAvailability<TData>(
            this MessageID feature,
            DiagnosticBag diagnostics,
            ParseOptions parseOptions,
            Func<TData, Location> getLocation,
            TData data)
        {
            if (GetFeatureAvailabilityDiagnosticInfo(feature, (CSharpParseOptions)parseOptions) is { } diagInfo)
            {
                diagnostics.Add(diagInfo, getLocation(data));
                return false;
            }
            return true;
        }

        private static bool CheckFeatureAvailability<TData>(
            this MessageID feature,
            BindingDiagnosticBag diagnostics,
            ParseOptions parseOptions,
            Func<TData, Location> getLocation,
            TData data)
        {
            if (GetFeatureAvailabilityDiagnosticInfo(feature, (CSharpParseOptions)parseOptions) is { } diagInfo)
            {
                diagnostics.Add(diagInfo, getLocation(data));
                return false;
            }
            return true;
        }

        internal static bool CheckFeatureAvailability(
            this MessageID feature,
            BindingDiagnosticBag diagnostics,
            Compilation compilation,
            Location location)
        {
            if (GetFeatureAvailabilityDiagnosticInfo(feature, (CSharpCompilation)compilation) is { } diagInfo)
            {
                diagnostics.Add(diagInfo, location);
                return false;
            }
            return true;
        }

        internal static CSDiagnosticInfo? GetFeatureAvailabilityDiagnosticInfo(this MessageID feature, CSharpParseOptions options)
            => options.IsFeatureEnabled(feature) ? null : GetDisabledFeatureDiagnosticInfo(feature, options.LanguageVersion);

        internal static CSDiagnosticInfo? GetFeatureAvailabilityDiagnosticInfo(this MessageID feature, CSharpCompilation compilation)
            => compilation.IsFeatureEnabled(feature) ? null : GetDisabledFeatureDiagnosticInfo(feature, compilation.LanguageVersion);

        private static CSDiagnosticInfo GetDisabledFeatureDiagnosticInfo(MessageID feature, LanguageVersion availableVersion)
        {
            string? requiredFeature = feature.RequiredFeature();
            if (requiredFeature != null)
            {
                return new CSDiagnosticInfo(ErrorCode.ERR_FeatureIsExperimental, feature.Localize(), requiredFeature);
            }

            LanguageVersion requiredVersion = feature.RequiredVersion();
            return requiredVersion == LanguageVersion.Preview.MapSpecifiedToEffectiveVersion()
                ? new CSDiagnosticInfo(ErrorCode.ERR_FeatureInPreview, feature.Localize())
                : new CSDiagnosticInfo(availableVersion.GetErrorCode(), feature.Localize(), new CSharpRequiredLanguageVersion(requiredVersion));
        }

        internal static LanguageVersion RequiredVersion(this MessageID feature)
        {
            Debug.Assert(RequiredFeature(feature) == null);

            // Based on CSourceParser::GetFeatureUsage from SourceParser.cpp.
            // Checks are in the LanguageParser unless otherwise noted.
            switch (feature)
            {
                // PREFER reporting diagnostics in binding when diagnostics do not affect the shape of the syntax tree

                // C# preview features.
                case MessageID.IDS_FeatureCollectionExpressionArguments:
                case MessageID.IDS_FeatureUnsafeEvolution: // https://github.com/dotnet/roslyn/issues/82546: keep this in preview until C# 16
                case MessageID.IDS_FeatureUnions:
                case MessageID.IDS_FeatureStaticMembersInInterfaces:
                case MessageID.IDS_FeatureClosedClasses: // semantic check
                case MessageID.IDS_FeatureLabeledBreakContinue:
                case MessageID.IDS_FeatureExtensionIndexers:
                    return LanguageVersion.Preview;

                // C# 14.0 features.
                case MessageID.IDS_FeatureFieldKeyword:
                case MessageID.IDS_FeatureFirstClassSpan:
                case MessageID.IDS_FeatureUnboundGenericTypesInNameof:
                case MessageID.IDS_FeatureSimpleLambdaParameterModifiers:
                case MessageID.IDS_FeaturePartialEventsAndConstructors:
                case MessageID.IDS_FeatureExtensions:
                case MessageID.IDS_FeatureNullConditionalAssignment:
                case MessageID.IDS_FeatureExpressionOptionalAndNamedArguments:
                case MessageID.IDS_FeatureUserDefinedCompoundAssignmentOperators:
                    return LanguageVersion.CSharp14;

                // C# 13.0 features.
                case MessageID.IDS_FeatureStringEscapeCharacter: // lexer check
                case MessageID.IDS_FeatureImplicitIndexerInitializer:
                case MessageID.IDS_FeatureLockObject:
                case MessageID.IDS_FeatureParamsCollections:
                case MessageID.IDS_FeatureRefUnsafeInIteratorAsync:
                case MessageID.IDS_FeatureRefStructInterfaces:
                case MessageID.IDS_FeatureAllowsRefStructConstraint:
                case MessageID.IDS_FeaturePartialProperties:
                case MessageID.IDS_FeatureOverloadResolutionPriority:
                    return LanguageVersion.CSharp13;

                // C# 12.0 features.
                case MessageID.IDS_FeatureLambdaOptionalParameters: // semantic check
                case MessageID.IDS_FeatureLambdaParamsArray: // semantic check
                case MessageID.IDS_FeaturePrimaryConstructors: // declaration table check
                case MessageID.IDS_FeatureUsingTypeAlias: // semantic check
                case MessageID.IDS_FeatureInstanceMemberInNameof: // semantic check
                case MessageID.IDS_FeatureInlineArrays: // semantic check
                case MessageID.IDS_FeatureCollectionExpressions: // semantic check
                case MessageID.IDS_FeatureRefReadonlyParameters: // semantic check
                    return LanguageVersion.CSharp12;

                // C# 11.0 features.
                case MessageID.IDS_FeatureRawStringLiterals:
                case MessageID.IDS_FeatureStaticAbstractMembersInInterfaces: // semantic check
                case MessageID.IDS_FeatureNewLinesInInterpolations: // semantic check
                case MessageID.IDS_FeatureListPattern: // semantic check
                case MessageID.IDS_FeatureRequiredMembers: // semantic check
                case MessageID.IDS_FeatureCacheStaticMethodGroupConversion: // lowering check
                case MessageID.IDS_FeatureSpanCharConstantPattern:
                case MessageID.IDS_FeatureAutoDefaultStructs: // semantic check
                case MessageID.IDS_FeatureCheckedUserDefinedOperators: // semantic check for declarations, parsing check for doc comments
                case MessageID.IDS_FeatureUtf8StringLiterals: // semantic check
                case MessageID.IDS_FeatureUnsignedRightShift: // semantic check for declarations and consumption, parsing check for doc comments
                case MessageID.IDS_FeatureRelaxedShiftOperator: // semantic check
                case MessageID.IDS_FeatureRefFields: // semantic check
                case MessageID.IDS_FeatureFileTypes: // semantic check
                case MessageID.IDS_FeatureGenericAttributes: // semantic check
                    return LanguageVersion.CSharp11;

                // C# 10.0 features.
                case MessageID.IDS_FeatureMixedDeclarationsAndExpressionsInDeconstruction: // semantic check
                case MessageID.IDS_FeatureSealedToStringInRecord: // semantic check
                case MessageID.IDS_FeatureImprovedInterpolatedStrings: // semantic check
                case MessageID.IDS_FeatureRecordStructs:
                case MessageID.IDS_FeatureWithOnStructs: // semantic check
                case MessageID.IDS_FeatureWithOnAnonymousTypes: // semantic check
                case MessageID.IDS_FeaturePositionalFieldsInRecords: // semantic check
                case MessageID.IDS_FeatureGlobalUsing:
                case MessageID.IDS_FeatureInferredDelegateType: // semantic check
                case MessageID.IDS_FeatureLambdaAttributes: // semantic check
                case MessageID.IDS_FeatureExtendedPropertyPatterns: // semantic check
                case MessageID.IDS_FeatureLambdaReturnType: // semantic check
                case MessageID.IDS_AsyncMethodBuilderOverride: // semantic check
                case MessageID.IDS_FeatureConstantInterpolatedStrings: // semantic check
                case MessageID.IDS_FeatureImplicitImplementationOfNonPublicMembers: // semantic check
                case MessageID.IDS_FeatureFileScopedNamespace: // semantic check
                case MessageID.IDS_FeatureParameterlessStructConstructors: // semantic check
                case MessageID.IDS_FeatureStructFieldInitializers: // semantic check
                    return LanguageVersion.CSharp10;

                // C# 9.0 features.
                case MessageID.IDS_FeatureLambdaDiscardParameters: // semantic check
                case MessageID.IDS_FeatureFunctionPointers: // semantic check
                case MessageID.IDS_FeatureLocalFunctionAttributes: // syntax check
                case MessageID.IDS_FeatureExternLocalFunctions: // semantic check
                case MessageID.IDS_FeatureImplicitObjectCreation: // semantic check
                case MessageID.IDS_FeatureMemberNotNull:
                case MessageID.IDS_FeatureAndPattern: // semantic check
                case MessageID.IDS_FeatureNotPattern: // semantic check
                case MessageID.IDS_FeatureOrPattern: // semantic check
                case MessageID.IDS_FeatureParenthesizedPattern: // semantic check
                case MessageID.IDS_FeatureTypePattern: // semantic check
                case MessageID.IDS_FeatureRelationalPattern: // semantic check
                case MessageID.IDS_FeatureExtensionGetEnumerator: // semantic check
                case MessageID.IDS_FeatureExtensionGetAsyncEnumerator: // semantic check
                case MessageID.IDS_FeatureNativeInt:
                case MessageID.IDS_FeatureExtendedPartialMethods: // semantic check
                case MessageID.IDS_TopLevelStatements:
                case MessageID.IDS_FeatureInitOnlySetters: // semantic check
                case MessageID.IDS_FeatureRecords: // semantic check
                case MessageID.IDS_FeatureTargetTypedConditional:  // semantic check
                case MessageID.IDS_FeatureCovariantReturnsForOverrides: // semantic check
                case MessageID.IDS_FeatureStaticAnonymousFunction: // semantic check
                case MessageID.IDS_FeatureModuleInitializers: // semantic check on method attribute
                case MessageID.IDS_FeatureDefaultTypeParameterConstraint: // semantic check
                case MessageID.IDS_FeatureVarianceSafetyForStaticInterfaceMembers: // semantic check
                    return LanguageVersion.CSharp9;

                // C# 8.0 features.
                case MessageID.IDS_FeatureAltInterpolatedVerbatimStrings: // semantic check
                case MessageID.IDS_FeatureCoalesceAssignmentExpression: // semantic check
                case MessageID.IDS_FeatureUnconstrainedTypeParameterInNullCoalescingOperator:
                case MessageID.IDS_FeatureNullableReferenceTypes: // syntax and semantic check
                case MessageID.IDS_FeatureIndexOperator: // semantic check
                case MessageID.IDS_FeatureRangeOperator: // semantic check
                case MessageID.IDS_FeatureAsyncStreams: // semantic check
                case MessageID.IDS_FeatureRecursivePatterns: // semantic check
                case MessageID.IDS_FeatureUsingDeclarations: // semantic check
                case MessageID.IDS_FeatureDisposalPattern: //semantic check
                case MessageID.IDS_FeatureStaticLocalFunctions: // semantic check
                case MessageID.IDS_FeatureNameShadowingInNestedFunctions:
                case MessageID.IDS_FeatureUnmanagedConstructedTypes: // semantic check
                case MessageID.IDS_FeatureObsoleteOnPropertyAccessor:
                case MessageID.IDS_FeatureReadOnlyMembers:
                case MessageID.IDS_DefaultInterfaceImplementation: // semantic check
                case MessageID.IDS_OverrideWithConstraints: // semantic check
                case MessageID.IDS_FeatureNestedStackalloc: // semantic check
                case MessageID.IDS_FeatureNotNullGenericTypeConstraint:// semantic check
                case MessageID.IDS_FeatureSwitchExpression:
                case MessageID.IDS_FeatureAsyncUsing:
                case MessageID.IDS_FeatureNullPointerConstantPattern: //semantic check
                    return LanguageVersion.CSharp8;

                // C# 7.3 features.
                case MessageID.IDS_FeatureAttributesOnBackingFields: // semantic check
                case MessageID.IDS_FeatureImprovedOverloadCandidates: // semantic check
                case MessageID.IDS_FeatureTupleEquality: // semantic check
                case MessageID.IDS_FeatureRefReassignment: // semantic check
                case MessageID.IDS_FeatureRefFor:
                case MessageID.IDS_FeatureRefForEach: // semantic check
                case MessageID.IDS_FeatureEnumGenericTypeConstraint: // semantic check
                case MessageID.IDS_FeatureDelegateGenericTypeConstraint: // semantic check
                case MessageID.IDS_FeatureUnmanagedGenericTypeConstraint: // semantic check
                case MessageID.IDS_FeatureStackAllocInitializer: // semantic check
                case MessageID.IDS_FeatureExpressionVariablesInQueriesAndInitializers: // semantic check
                case MessageID.IDS_FeatureExtensibleFixedStatement:  // semantic check
                case MessageID.IDS_FeatureIndexingMovableFixedBuffers: //semantic check
                    return LanguageVersion.CSharp7_3;

                // C# 7.2 features.
                case MessageID.IDS_FeatureNonTrailingNamedArguments: // semantic check
                case MessageID.IDS_FeatureLeadingDigitSeparator:
                case MessageID.IDS_FeaturePrivateProtected:
                case MessageID.IDS_FeatureReadOnlyReferences: // semantic check
                case MessageID.IDS_FeatureRefStructs: // semantic check
                case MessageID.IDS_FeatureReadOnlyStructs: // semantic check
                case MessageID.IDS_FeatureRefExtensionMethods:
                case MessageID.IDS_FeatureRefConditional:
                    return LanguageVersion.CSharp7_2;

                // C# 7.1 features.
                case MessageID.IDS_FeatureAsyncMain:
                case MessageID.IDS_FeatureDefaultLiteral: // semantic check
                case MessageID.IDS_FeatureInferredTupleNames:
                case MessageID.IDS_FeatureGenericPatternMatching:
                    return LanguageVersion.CSharp7_1;

                // C# 7 features.
                case MessageID.IDS_FeatureBinaryLiteral:
                case MessageID.IDS_FeatureDigitSeparator:
                case MessageID.IDS_FeatureLocalFunctions: // semantic check
                case MessageID.IDS_FeatureRefLocalsReturns:
                case MessageID.IDS_FeaturePatternMatching: // semantic check
                case MessageID.IDS_FeatureThrowExpression: // semantic check
                case MessageID.IDS_FeatureTuples:
                case MessageID.IDS_FeatureOutVar: // semantic check
                case MessageID.IDS_FeatureExpressionBodiedAccessor:
                case MessageID.IDS_FeatureExpressionBodiedDeOrConstructor:
                case MessageID.IDS_FeatureDiscards:
                    return LanguageVersion.CSharp7;

                // C# 6 features.
                case MessageID.IDS_FeatureExceptionFilter: // semantic check
                case MessageID.IDS_FeatureAutoPropertyInitializer: // semantic check
                case MessageID.IDS_FeatureNullPropagatingOperator: // semantic check
                case MessageID.IDS_FeatureExpressionBodiedMethod:
                case MessageID.IDS_FeatureExpressionBodiedProperty: // semantic check
                case MessageID.IDS_FeatureExpressionBodiedIndexer: // semantic check
                case MessageID.IDS_FeatureNameof:
                case MessageID.IDS_FeatureDictionaryInitializer: // semantic check
                case MessageID.IDS_FeatureUsingStatic: // semantic check
                case MessageID.IDS_FeatureInterpolatedStrings: // semantic check
                case MessageID.IDS_AwaitInCatchAndFinally:
                case MessageID.IDS_FeatureReadonlyAutoImplementedProperties:
                    return LanguageVersion.CSharp6;

                // C# 5 features.
                case MessageID.IDS_FeatureAsync: // semantic check
                    return LanguageVersion.CSharp5;

                // C# 4 features.
                case MessageID.IDS_FeatureDynamic: // Checked in the binder.
                case MessageID.IDS_FeatureTypeVariance: // semantic check
                case MessageID.IDS_FeatureNamedArgument: // semantic check
                case MessageID.IDS_FeatureOptionalParameter: // semantic check
                    return LanguageVersion.CSharp4;

                // C# 3 features.
                case MessageID.IDS_FeatureImplicitArray: // semantic check
                case MessageID.IDS_FeatureAnonymousTypes: // semantic check
                case MessageID.IDS_FeatureObjectInitializer:
                case MessageID.IDS_FeatureCollectionInitializer:
                case MessageID.IDS_FeatureLambda: // semantic check
                case MessageID.IDS_FeatureQueryExpression: // semantic check
                case MessageID.IDS_FeatureExtensionMethod:
                case MessageID.IDS_FeaturePartialMethod: // semantic check
                case MessageID.IDS_FeatureImplicitLocal: // Checked in the binder.
                case MessageID.IDS_FeatureAutoImplementedProperties:
                    return LanguageVersion.CSharp3;

                // C# 2 features.
                case MessageID.IDS_FeatureGenerics: // Also affects crefs.
                case MessageID.IDS_FeatureAnonDelegates: // semantic check
                case MessageID.IDS_FeatureGlobalNamespace: // Also affects crefs.
                case MessageID.IDS_FeatureFixedBuffer: // semantic check
                case MessageID.IDS_FeatureStaticClasses: // semantic check
                case MessageID.IDS_FeaturePartialTypes: // semantic check
                case MessageID.IDS_FeaturePropertyAccessorMods:
                case MessageID.IDS_FeatureExternAlias: // semantic check
                case MessageID.IDS_FeatureIterators: // semantic check
                case MessageID.IDS_FeatureDefault: // semantic check
                case MessageID.IDS_FeatureNullable:
                case MessageID.IDS_FeaturePragma: // Checked in the directive parser.
                case MessageID.IDS_FeatureSwitchOnBool: // Checked in the binder.
                    return LanguageVersion.CSharp2;

                // Special C# 2 feature: only a warning in C# 1.
                case MessageID.IDS_FeatureModuleAttrLoc:
                    return LanguageVersion.CSharp1;

                default:
                    throw ExceptionUtilities.UnexpectedValue(feature);
            }
        }
    }
}