cmd/compile: reject embedded unsafe.Pointer values

Fixes #14729

Change-Id: Ied819aa7b23e25de30aa8cde049c97297b4cab11
Reviewed-on: https://go-review.googlesource.com/22325Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/dcl.go

@@ -719,7 +719,7 @@ func checkembeddedtype(t *Type) {
 		}
 	}
 
-	if t.IsPtr() {
+	if t.IsPtr() || t.IsUnsafePtr() {
 		Yyerror("embedded type cannot be a pointer")
 	} else if t.Etype == TFORW && t.ForwardType().Embedlineno == 0 {
 		t.ForwardType().Embedlineno = lineno

src/cmd/compile/internal/gc/type.go

@@ -1111,6 +1111,11 @@ func (t *Type) IsPtr() bool {
 	return t.Etype == TPTR32 || t.Etype == TPTR64
 }
 
+// IsUnsafePtr reports whether t is an unsafe pointer.
+func (t *Type) IsUnsafePtr() bool {
+	return t.Etype == TUNSAFEPTR
+}
+
 // IsPtrShaped reports whether t is represented by a single machine pointer.
 // In addition to regular Go pointer types, this includes map, channel, and
 // function types and unsafe.Pointer. It does not include array or struct types

src/cmd/compile/internal/gc/typecheck.go

@@ -3557,7 +3557,7 @@ func copytype(n *Node, t *Type) {
 
 	if embedlineno != 0 {
 		lineno = embedlineno
-		if t.IsPtr() {
+		if t.IsPtr() || t.IsUnsafePtr() {
 			Yyerror("embedded type cannot be a pointer")
 		}
 	}

test/fixedbugs/issue14729.go

+// errorcheck
+
+// Copyright 2016 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.
+
+// Issue 14729: structs cannot embed unsafe.Pointer per the spec.
+
+package main
+
+import "unsafe"
+
+type s struct { unsafe.Pointer } // ERROR "embedded type cannot be a pointer"
+type s1 struct { p unsafe.Pointer }