Migrate block 163 to Dart 2.0.

tests/language_2/unnamed_closure_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.
 
 import "package:expect/expect.dart";
 
 getNonArray() => new A();
 
 class A {
   operator [](index) => index;
 }
 
 main() {
   Expect.equals(42, () {
     var res;
     do {
       var a = getNonArray();
       res = a[42];
     } while (false);
     return res;
   }());
 }