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cmd/compile: fix conversions from TypeParam to interface
If the TypeParam has all the methods of an interface, allow conversions from TypeParam to interface Fixes #47708 Change-Id: I40a82a31f6ea9354130dbe3bcfc83537094bf12c Reviewed-on: https://go-review.googlesource.com/c/go/+/342509 Reviewed-by: Dan Scales <danscales@google.com> Reviewed-by: Robert Griesemer <gri@golang.org> Trust: Dan Scales <danscales@google.com> Trust: Keith Randall <khr@golang.org> Trust: Robert Griesemer <gri@golang.org> Run-TryBot: Robert Griesemer <gri@golang.org> TryBot-Result: Go Bot <gobot@golang.org>
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@ -740,9 +740,16 @@ func implements(t, iface *types.Type, m, samename **types.Field, ptr *int) bool
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if t.IsInterface() || t.IsTypeParam() {
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if t.IsTypeParam() {
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// A typeparam satisfies an interface if its type bound
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// has all the methods of that interface.
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t = t.Bound()
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// If t is a simple type parameter T, its type and underlying is the same.
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// If t is a type definition:'type P[T any] T', its type is P[T] and its
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// underlying is T. Therefore we use 't.Underlying() != t' to distinguish them.
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if t.Underlying() != t {
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CalcMethods(t)
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} else {
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// A typeparam satisfies an interface if its type bound
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// has all the methods of that interface.
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t = t.Bound()
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}
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}
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i := 0
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tms := t.AllMethods().Slice()
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40
test/typeparam/issue47708.go
Normal file
40
test/typeparam/issue47708.go
Normal file
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@ -0,0 +1,40 @@
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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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import (
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"fmt"
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)
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type FooType[T any] interface {
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Foo(BarType[T])string
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}
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type BarType[T any] interface {
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Bar(FooType[T])string
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}
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type Baz[T any] T
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func (l Baz[T]) Foo(v BarType[T]) string {
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return v.Bar(l)
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}
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type Bob[T any] T
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func (l Bob[T]) Bar(v FooType[T]) string {
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if v,ok := v.(Baz[T]);ok{
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return fmt.Sprintf("%v%v",v,l)
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}
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return ""
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}
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func main() {
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var baz Baz[int] = 123
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var bob Bob[int] = 456
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if got, want := baz.Foo(bob), "123456"; got != want {
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panic(fmt.Sprintf("got %s want %s", got, want))
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}
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}
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