gc: Better error message for range over non-receive channel.

Fixes #2354

R=rsc
CC=golang-dev
https://golang.org/cl/5346044

src/cmd/gc/range.c

@@ -46,6 +46,10 @@ typecheckrange(Node *n)
 		break;
 
 	case TCHAN:
+		if(!(t->chan & Crecv)) {
+			yyerror("invalid operation: range %N (receive from send-only type %T)", n->right, n->right->type);
+			goto out;
+		}
 		t1 = t->type;
 		t2 = nil;
 		if(count(n->list) == 2)

test/chan/perm.go

@@ -48,7 +48,10 @@ func main() {
 	case x := <-cs: // ERROR "receive"
 		_ = x
 	}
-	
+
+	for _ = range cs {// ERROR "receive"
+	}
+
 	close(c)
 	close(cs)
 	close(cr)  // ERROR "receive"