cmd/compile: add missing Unalias call when writing type alias

Fixes #65778

Change-Id: I93af42967c7976d63b4f460b7ffbcb9a9c05ffe7
Reviewed-on: https://go-review.googlesource.com/c/go/+/565995
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>

src/cmd/compile/internal/noder/writer.go

@@ -831,7 +831,7 @@ func (w *writer) doObj(wext *writer, obj types2.Object) pkgbits.CodeObj {
 	case *types2.TypeName:
 		if obj.IsAlias() {
 			w.pos(obj)
-			w.typ(obj.Type())
+			w.typ(types2.Unalias(obj.Type()))
 			return pkgbits.ObjAlias
 		}
 

test/fixedbugs/issue65778.go

@@ -0,0 +1,13 @@
+// compile -godebug gotypesalias=1
+
+// 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 = int
+
+type T[P any] *A
+
+var _ T[int]