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https://github.com/golang/go
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e24977d231
The next CL will remove the -G flag, effectively hard-coding it to its current default (-G=3). Change-Id: Ib4743b529206928f9f1cca9fdb19989728327831 Reviewed-on: https://go-review.googlesource.com/c/go/+/388534 Reviewed-by: Keith Randall <khr@golang.org> Trust: Matthew Dempsky <mdempsky@google.com> Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
65 lines
1.3 KiB
Go
65 lines
1.3 KiB
Go
// run
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Test for cases where certain instantiations of a generic function (F in this
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// example) will always fail on a type assertion or mismatch on a type case.
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package main
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import "fmt"
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type S struct{}
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func (S) M() byte {
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return 0
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}
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type I[T any] interface {
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M() T
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}
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func F[T, A any](x I[T], shouldMatch bool) {
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switch x.(type) {
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case A:
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if !shouldMatch {
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fmt.Printf("wanted mis-match, got match")
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}
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default:
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if shouldMatch {
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fmt.Printf("wanted match, got mismatch")
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}
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}
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_, ok := x.(A)
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if ok != shouldMatch {
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fmt.Printf("ok: got %v, wanted %v", ok, shouldMatch)
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}
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if !shouldMatch {
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defer func() {
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if shouldMatch {
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fmt.Printf("Shouldn't have panicked")
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}
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recover()
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}()
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}
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_ = x.(A)
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if !shouldMatch {
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fmt.Printf("Should have panicked")
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}
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}
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func main() {
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// Test instantiation where the type switch/type asserts can't possibly succeed
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// (since string does not implement I[byte]).
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F[byte, string](S{}, false)
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// Test instantiation where the type switch/type asserts should succeed
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// (since S does implement I[byte])
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F[byte, S](S{}, true)
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F[byte, S](I[byte](S{}), true)
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}
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