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

tests/isolate/serialization_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.
 
 // Dart test program for testing serialization of messages without spawning
 // isolates.
 
 // ---------------------------------------------------------------------------
 // Serialization test.
 // ---------------------------------------------------------------------------
@@ skipping 26 matching lines @@
 
   var port = new ReceivePort();
   Expect.throws(() => f(port));
   port.close();
 
   var a = [ 1, 3, 5 ];
   var b = { 'b': 49 };
   var c = [ a, b, a, b, a ];
   var copied = f(c);
   verify(c, copied);
-  Expect.isFalse(c === copied);
-  Expect.isTrue(copied[0] === copied[2]);
-  Expect.isTrue(copied[0] === copied[4]);
-  Expect.isTrue(copied[1] === copied[3]);
+  Expect.isFalse(identical(c, copied));
+  Expect.identical(copied[0], copied[2]);
+  Expect.identical(copied[0], copied[4]);
+  Expect.identical(copied[1], copied[3]);
 }
 
 void copyAndVerify(o, Function f) {
   var copy = f(o);
   verify(o, copy);
 }
 
 void verify(o, copy) {
   if ((o is bool) || (o is num) || (o is String)) {
     Expect.equals(o, copy);
   } else if (o is List) {
     Expect.isTrue(copy is List);
     Expect.equals(o.length, copy.length);
     for (int i = 0; i < o.length; i++) {
       verify(o[i], copy[i]);
     }
   } else if (o is Map) {
     Expect.isTrue(copy is Map);
     Expect.equals(o.length, copy.length);
     o.forEach((key, value) {
       Expect.isTrue(copy.containsKey(key));
       verify(value, copy[key]);
     });
   } else {
     Expect.fail("Unexpected object encountered");
   }
 }