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