go/types, types2: unalias tilde terms in underIs

Unalias the ~T terms during underIs. Before, if T was an alias of U, it may pass T to the iteration function. The iterator function expects an underlying type, under(U), to be passed. This caused several bugs where underIs is used without eventually taking the underlying type. Updates #68935 Fixes #68903 Change-Id: Ie8691d8dddaea00e1dcba94d17c0f1b021fc49a2 Reviewed-on: https://go-review.googlesource.com/c/go/+/606075 Reviewed-by: Robert Griesemer <gri@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Robert Findley <rfindley@google.com>
golang · Aug 20, 2024 · 1a90dcd · 1a90dcd
1 parent 6fb6ace
commit 1a90dcd
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Showing 4 changed files with 54 additions and 4 deletions.
diff --git a/src/cmd/compile/internal/types2/typeset.go b/src/cmd/compile/internal/types2/typeset.go
@@ -131,8 +131,8 @@ func (s *_TypeSet) underIs(f func(Type) bool) bool {
 	}
 	for _, t := range s.terms {
 		assert(t.typ != nil)
-		// x == under(x) for ~x terms
-		u := t.typ
+		// Unalias(x) == under(x) for ~x terms
+		u := Unalias(t.typ)
 		if !t.tilde {
 			u = under(u)
 		}

diff --git a/src/go/types/typeset.go b/src/go/types/typeset.go
diff --git a/src/internal/types/testdata/fixedbugs/issue68903.go b/src/internal/types/testdata/fixedbugs/issue68903.go
@@ -0,0 +1,24 @@
+// Copyright 2024 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 p
+
+type A = [4]int
+type B = map[string]interface{}
+
+func _[T ~A](x T) {
+	_ = len(x)
+}
+
+func _[U ~A](x U) {
+	_ = cap(x)
+}
+
+func _[V ~A]() {
+	_ = V{}
+}
+
+func _[W ~B](a interface{}) {
+	_ = a.(W)["key"]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue68935.go b/src/internal/types/testdata/fixedbugs/issue68935.go
@@ -0,0 +1,26 @@
+// Copyright 2024 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 p
+
+type A = struct {
+	F string
+	G int
+}
+
+func Make[T ~A]() T {
+	return T{
+		F: "blah",
+		G: 1234,
+	}
+}
+
+type N struct {
+	F string
+	G int
+}
+
+func _() {
+	_ = Make[N]()
+}