mirror of
https://github.com/golang/go
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48 lines
701 B
Go
48 lines
701 B
Go
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// run -gcflags=-G=3
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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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package main
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type I[T any] interface {
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foo()
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}
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type J[T any] interface {
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foo()
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bar()
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}
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//go:noinline
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func f[T J[T]](x T, g func(T) T) I[T] {
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// contains a cast between two nonempty interfaces
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// Also make sure we don't evaluate g(x) twice.
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return I[T](J[T](g(x)))
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}
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type S struct {
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x int
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}
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func (s *S) foo() {}
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func (s *S) bar() {}
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var cnt int
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func inc(s *S) *S {
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cnt++
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return s
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}
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func main() {
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i := f(&S{x: 7}, inc)
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if i.(*S).x != 7 {
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panic("bad")
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}
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if cnt != 1 {
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panic("multiple calls")
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}
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}
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