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https://github.com/golang/go
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6a35e07512
Conversions need to allow nil through. We do that using a CONVIFACE instead of a DOTTYPE. Also reorganize how nonempty interfaces are handled. For nonempty to empty, a simple CONVIFACE suffices. For nonempty to nonempty, we need to call the runtime to get the new itab. Use the entry from the dictionary to identify the target interface type (if parameterized). Fixes #47925 Change-Id: I4ffeed964318bb3e270b06f558e6ab9c5bfc7188 Reviewed-on: https://go-review.googlesource.com/c/go/+/344830 Trust: Keith Randall <khr@golang.org> Trust: Dan Scales <danscales@google.com> Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Dan Scales <danscales@google.com>
48 lines
701 B
Go
48 lines
701 B
Go
// 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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