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master
test/typeswitch3.go
56 строк
999 B
Robert Griesemer
cmd/compile/internal/types2: better error for type assertion/switch on type parameter value
13 ноя 2021, 01:20
13 ноя 2021, 01:20
f9dcda3
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// errorcheck // Copyright 2011 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // Verify that erroneous type switches are caught by the compiler. // Issue 2700, among other things. // Does not compile. package main import ( "io" ) type I interface { M() } func main() { var x I switch x.(type) { case string: // ERROR "impossible" println("FAIL") } // Issue 2700: if the case type is an interface, nothing is impossible var r io.Reader _, _ = r.(io.Writer) switch r.(type) { case io.Writer: } // Issue 2827. switch _ := r.(type) { // ERROR "invalid variable name _|no new variables?" } } func noninterface() { var i int switch i.(type) { // ERROR "cannot type switch on non-interface value|not an interface" case string: case int: } type S struct { name string } var s S switch s.(type) { // ERROR "cannot type switch on non-interface value|not an interface" } }