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

tests/isolate/mandel_isolate_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.
 
 library MandelIsolateTest;
 import 'dart:isolate';
 import 'dart:math';
 import '../../pkg/unittest/lib/unittest.dart';
 
 const TERMINATION_MESSAGE = -1;
@@ skipping 21 matching lines @@
     _validated = new Completer<bool>();
   }
 
   void startClient(int id) {
     assert(_sent < N);
     final client = new LineProcessorClient(this, id);
     client.processLine(_sent++);
   }
 
   void notifyProcessedLine(LineProcessorClient client, int y, List<int> line) {
-    assert(_result[y] === null);
+    assert(_result[y] == null);
     _result[y] = line;
     _lineProcessedBy[y] = client;
 
     if (_sent != N) {
       client.processLine(_sent++);
     } else {
       client.shutdown();
     }
 
     // If all lines have been computed, validate the result.
@@ skipping 80 matching lines @@
 void processLines() {
   port.receive((message, SendPort replyTo) {
     if (message == TERMINATION_MESSAGE) {
       assert(replyTo == null);
       port.close();
     } else {
       replyTo.send(processLine(message), null);
     }
   });
 }