зеркало из https://github.com/CryptoPro/go.git
65 строки
1.3 KiB
Go
65 строки
1.3 KiB
Go
// run -gcflags=-G=3
|
|
|
|
// Copyright 2021 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.
|
|
|
|
// Test for cases where certain instantiations of a generic function (F in this
|
|
// example) will always fail on a type assertion or mismatch on a type case.
|
|
|
|
package main
|
|
|
|
import "fmt"
|
|
|
|
type S struct{}
|
|
|
|
func (S) M() byte {
|
|
return 0
|
|
}
|
|
|
|
type I[T any] interface {
|
|
M() T
|
|
}
|
|
|
|
func F[T, A any](x I[T], shouldMatch bool) {
|
|
switch x.(type) {
|
|
case A:
|
|
if !shouldMatch {
|
|
fmt.Printf("wanted mis-match, got match")
|
|
}
|
|
default:
|
|
if shouldMatch {
|
|
fmt.Printf("wanted match, got mismatch")
|
|
}
|
|
}
|
|
|
|
_, ok := x.(A)
|
|
if ok != shouldMatch {
|
|
fmt.Printf("ok: got %v, wanted %v", ok, shouldMatch)
|
|
}
|
|
|
|
if !shouldMatch {
|
|
defer func() {
|
|
if shouldMatch {
|
|
fmt.Printf("Shouldn't have panicked")
|
|
}
|
|
recover()
|
|
}()
|
|
}
|
|
_ = x.(A)
|
|
if !shouldMatch {
|
|
fmt.Printf("Should have panicked")
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
// Test instantiation where the type switch/type asserts can't possibly succeed
|
|
// (since string does not implement I[byte]).
|
|
F[byte, string](S{}, false)
|
|
|
|
// Test instantiation where the type switch/type asserts should succeed
|
|
// (since S does implement I[byte])
|
|
F[byte, S](S{}, true)
|
|
F[byte, S](I[byte](S{}), true)
|
|
}
|