a === b -> identical(a, b)

tests/corelib/set_iterator_test.dart

 // Copyright (c) 2011, 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.
 
 class FixedHashCode {
   final int _hashCode;
   const FixedHashCode(this._hashCode);
   int get hashCode { return _hashCode; }
 }
 
@@ skipping 119 matching lines @@
 
   static void testDifferentHashCodes() {
     for (int i = -20; i < 20; i++) {
       Set set = new Set();
       var element = new FixedHashCode(i);
       set.add(element);
       Expect.equals(1, set.length);
       bool foundIt = false;
       for (var x in set) {
         foundIt = true;
-        Expect.equals(true, x === element);
+        Expect.equals(true, identical(x, element));
       }
       Expect.equals(true, foundIt);
     }
   }
 }
 
 main() {
   SetIteratorTest.testMain();
 }