gc: do not allow slice of array literal

R=ken2
CC=golang-dev
https://golang.org/cl/5440083

src/cmd/gc/typecheck.c

@@ -541,6 +541,7 @@ reswitch:
 		case OMAPLIT:
 		case OSTRUCTLIT:
 		case OARRAYLIT:
+			if(!n->implicit)
 				break;
 		default:
 			checklvalue(n->left, "take the address of");
@@ -757,9 +758,13 @@ reswitch:
 		defaultlit(&n->right->left, T);
 		defaultlit(&n->right->right, T);
 		if(isfixedarray(n->left->type)) {
+			if(!islvalue(n->left)) {
+				yyerror("invalid operation %N (slice of unaddressable value)", n);
+				goto error;
+			}
 			n->left = nod(OADDR, n->left, N);
 			n->left->implicit = 1;
-			typecheck(&n->left, top);
+			typecheck(&n->left, Erv);
 		}
 		if(n->right->left != N) {
 			if((t = n->right->left->type) == T)

test/complit1.go

+// errchk $G -e $D/$F.go
+
+// 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.
+
+package main
+
+var m map[int][3]int
+func f() [3]int
+
+func fp() *[3]int
+var mp map[int]*[3]int
+
+var (
+	_ = [3]int{1,2,3}[:]  // ERROR "slice of unaddressable value"
+	_ = m[0][:]  // ERROR "slice of unaddressable value"
+	_ = f()[:]  // ERROR "slice of unaddressable value"
+	
+	// these are okay because they are slicing a pointer to an array
+	_ = (&[3]int{1,2,3})[:]
+	_ = mp[0][:]
+	_ = fp()[:]
+)
\ No newline at end of file

test/fixedbugs/bug268.go

-// $G $D/$F.go && $L $F.$A && ./$A.out
-
-// Copyright 2010 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.
-
-// http://code.google.com/p/go/issues/detail?id=745
-
-package main
-
-type T1 struct {
-	T2 *T2
-}
-
-type T2 struct {
-	T3 *T3
-}
-
-type T3 struct {
-	T4 []*T4
-}
-
-type T4 struct {
-	X int
-}
-
-func f() *T1 {
-	x := &T1{
-		&T2{
-			&T3{
-				[1]*T4{
-					&T4{5},
-				}[0:],
-			},
-		},
-	}
-	return x
-}
-
-func g(x int) {
-	if x == 0 {
-		return
-	}
-	g(x-1)
-}
-
-func main() {
-	x := f()
-	g(100) // smash temporaries left over on stack
-	if x.T2.T3.T4[0].X != 5 {
-		println("BUG", x.T2.T3.T4[0].X)
-	}
-}