gc: disallow map/func equality via interface comparison

Missed when I removed direct map/func equality.

R=ken2
CC=golang-dev
https://golang.org/cl/5452052

src/cmd/gc/subr.c

@@ -499,8 +499,7 @@ algtype(Type *t)
 {
 	int a;
 
-	if(issimple[t->etype] || isptr[t->etype] ||
+	if(issimple[t->etype] || isptr[t->etype] || t->etype == TCHAN) {
-		t->etype == TCHAN || t->etype == TFUNC || t->etype == TMAP) {
 		if(t->width == 1)
 			a = AMEM8;
 		else if(t->width == 2)

src/pkg/reflect/all_test.go

@@ -468,8 +468,8 @@ func TestInterfaceValue(t *testing.T) {
 func TestFunctionValue(t *testing.T) {
 	var x interface{} = func() {}
 	v := ValueOf(x)
-	if v.Interface() != v.Interface() || v.Interface() != x {
+	if fmt.Sprint(v.Interface()) != fmt.Sprint(x) {
-		t.Fatalf("TestFunction != itself")
+		t.Fatalf("TestFunction returned wrong pointer")
 	}
 	assert(t, v.Type().String(), "func()")
 }

test/interface/noeq.go

@@ -0,0 +1,39 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: interface/noeq
+
+// Copyright 2011 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.
+
+// Interface values containing types that cannot be compared for equality.
+
+package main
+
+func main() {
+	cmp(1)
+	
+	var (
+		m map[int]int
+		s struct{}
+		f func()
+	)
+	noCmp(m)
+	noCmp(s)
+	noCmp(f)
+}
+
+func cmp(x interface{}) bool {
+	return x == x
+}
+
+func noCmp(x interface{}) {
+	shouldPanic(func() { cmp(x) })
+}
+
+func shouldPanic(f func()) {
+	defer func() {
+		if recover() == nil {
+			panic("function should panic")
+		}
+	}()
+	f()
+}