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cmd/compile: deal with blank nodes with typeparam type during stenciling

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Deal correctly with a blank local variable with type param type. This is
a special case, because a blank local variable is not in the fn.Dcl
list. In this case, we must explicitly create a new blank node with the
correct substituted type, so we have correct types if the blank local
variable has an initializing assignment.

Fixes #48602

Change-Id: I903ea44b29934e180404e32800773b7309bf297b
Reviewed-on: https://go-review.googlesource.com/c/go/+/352117
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Trust: Dan Scales <danscales@google.com>
This commit is contained in:
Dan Scales 2021-09-24 08:57:06 -07:00
parent d60ad1e068
commit 8854368cb0
2 changed files with 31 additions and 0 deletions
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6
src/cmd/compile/internal/noder/stencil.go
View File

@ -912,6 +912,12 @@ func (subst *subster) node(n ir.Node) ir.Node {
if v := subst.ts.Vars[x.(*ir.Name)]; v != nil {
return v
}
if ir.IsBlank(x) {
// Special case, because a blank local variable is
// not in the fn.Dcl list.
m := ir.NewNameAt(x.Pos(), ir.BlankNode.Sym())
return typed(subst.ts.Typ(x.Type()), m)
}
return x
case ir.ONONAME:
// This handles the identifier in a type switch guard

25
test/typeparam/issue48602.go Normal file
View File

@ -0,0 +1,25 @@
// 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 Iterator[T any] interface {
Iterate(fn T)
}
type IteratorFunc[T any] func(fn T)
func (f IteratorFunc[T]) Iterate(fn T) {
f(fn)
}
func Foo[R any]() {
var _ Iterator[R] = IteratorFunc[R](nil)
}
func main() {
Foo[int]()
}