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cmd/compile: fix conversions from TypeParam to interface

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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>
This commit is contained in:
korzhao 2021-08-16 22:25:47 +08:00 committed by Robert Griesemer
parent 717f337d1d
commit 5670ff4ae5
2 changed files with 50 additions and 3 deletions
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7
src/cmd/compile/internal/typecheck/subr.go
View File

@ -740,10 +740,17 @@ func implements(t, iface *types.Type, m, samename **types.Field, ptr *int) bool
if t.IsInterface() || t.IsTypeParam() {
if t.IsTypeParam() {
// If t is a simple type parameter T, its type and underlying is the same.
// If t is a type definition:'type P[T any] T', its type is P[T] and its
// underlying is T. Therefore we use 't.Underlying() != t' to distinguish them.
if t.Underlying() != t {
CalcMethods(t)
} else {
// A typeparam satisfies an interface if its type bound
// has all the methods of that interface.
t = t.Bound()
}
}
i := 0
tms := t.AllMethods().Slice()
for _, im := range iface.AllMethods().Slice() {

40
test/typeparam/issue47708.go Normal file
View File

@ -0,0 +1,40 @@
// 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
import (
"fmt"
)
type FooType[T any] interface {
Foo(BarType[T])string
}
type BarType[T any] interface {
Bar(FooType[T])string
}
type Baz[T any] T
func (l Baz[T]) Foo(v BarType[T]) string {
return v.Bar(l)
}
type Bob[T any] T
func (l Bob[T]) Bar(v FooType[T]) string {
if v,ok := v.(Baz[T]);ok{
return fmt.Sprintf("%v%v",v,l)
}
return ""
}
func main() {
var baz Baz[int] = 123
var bob Bob[int] = 456
if got, want := baz.Foo(bob), "123456"; got != want {
panic(fmt.Sprintf("got %s want %s", got, want))
}
}