gc: disallow [...][...]int{{1,2,3}}

Fixes #1600.

R=ken2
CC=golang-dev
https://golang.org/cl/4819045

src/cmd/gc/go.h

@@ -531,6 +531,7 @@ enum
 	Eindir = 1<<8,		// indirecting through expression
 	Eaddr = 1<<9,		// taking address of expression
 	Eproc = 1<<10,		// inside a go statement
+	Ecomplit = 1<<11,	// type in composite literal
 };
 
 #define	BITS	5

src/cmd/gc/typecheck.c

@@ -239,6 +239,8 @@ reswitch:
 			t->bound = -1;	// slice
 		} else if(l->op == ODDD) {
 			t->bound = -100;	// to be filled in
+			if(!(top&Ecomplit))
+				yyerror("use of [...] array outside of array literal");
 		} else {
 			l = typecheck(&n->left, Erv);
 			switch(consttype(l)) {
@@ -1342,11 +1344,6 @@ ret:
 		case TNIL:
 		case TBLANK:
 			break;
-		case TARRAY:
-			if(t->bound == -100) {
-				yyerror("use of [...] array outside of array literal");
-				t->bound = 1;
-			}
 		default:
 			checkwidth(t);
 		}
@@ -1971,7 +1968,7 @@ typecheckcomplit(Node **np)
 	}
 
 	setlineno(n->right);
-	l = typecheck(&n->right /* sic */, Etype);
+	l = typecheck(&n->right /* sic */, Etype|Ecomplit);
 	if((t = l->type) == T)
 		goto error;
 	nerr = nerrors;
@@ -2039,7 +2036,7 @@ typecheckcomplit(Node **np)
 				l->right->right = typenod(pushtype);
 			typecheck(&l->right, Erv);
 			defaultlit(&l->right, t->type);
-			l->right = assignconv(l->right, t->type, "array index");
+			l->right = assignconv(l->right, t->type, "array element");
 		}
 		if(t->bound == -100)
 			t->bound = len;

test/ddd1.go

@@ -44,4 +44,6 @@ func bad(args ...int) {
 	_ = unsafe.Pointer(&x...)	// ERROR "[.][.][.]"
 	_ = unsafe.Sizeof(x...)	// ERROR "[.][.][.]"
 	_ = [...]byte("foo") // ERROR "[.][.][.]"
+	_ = [...][...]int{{1,2,3},{4,5,6}}	// ERROR "[.][.][.]"
 }
+