Fix cascade_test

tests/language/cascade_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Test cascades.
 
 class A {
   int x;
   int y;
 
   A(this.x, this.y);
 
   A setX(int x) { this.x = x; return this; }
 
   void setY(int y) { this.y = y; }
 
   Function swap() {
     int tmp = x;
     x = y;
     y = tmp;
     return this.swap;
   }
 
   void check(int x, int y) {
     Expect.equals(x, this.x);
     Expect.equals(y, this.y);
   }
 
-  int operator[](var i) {
+  operator[](var i) {
     if (i == 0) return x;
     if (i == 1) return y;
     if (i == "swap") return this.swap;
     return null;
   }
 
   int operator[]=(int i, int value) {
     if (i == 0) {
       x = value;
     } else if (i == 1) {
@@ skipping 20 matching lines @@
    ..[0] = 2..check(2, 10)
    ..setX(10).setY(3)..check(10, 3)
    ..setX(7)["swap"]()..check(3, 7)
    ..import()..check(4, 7)
    ..["swap"]()()()..check(7, 4);
   a.check(7,4);
   a..(42);  /// 01: compile-time error
   a..37;  /// 02: compile-time error
   a.."foo";  /// 03: compile-time error
 }