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

utils/css/parser.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
 
 /**
  * A simple recursive descent parser for CSS.
  */
 class Parser {
   Tokenizer tokenizer;
 
   var _fs;                        // If non-null filesystem to read files.
@@ skipping 118 matching lines @@
     var message;
     try {
       message = 'expected $expected, but found $tok';
     } catch (e) {
       message = 'parsing error expected $expected';
     }
     _error(message, tok.span);
   }
 
   void _error(String message, [SourceSpan location=null]) {
-    if (location === null) {
+    if (location == null) {
       location = _peekToken.span;
     }
 
     if (_erroMsgRedirector == null) {
        world.fatal(message, location);    // syntax errors are fatal for now
     } else {
       String text = "";
       if (location != null) {
         text = location.toMessageString("");
       }
       _erroMsgRedirector.displayError("CSS error: \r${text}\r${message}");
     }
   }
 
   void _warning(String message, [SourceSpan location=null]) {
-    if (location === null) {
+    if (location == null) {
       location = _peekToken.span;
     }
 
     world.warning(message, location);
   }
 
   SourceSpan _makeSpan(int start) {
     return new SourceSpan(source, start, _previousToken.end);
   }
 
@@ skipping 842 matching lines @@
 
     return result;
   }
 }
 
 /** Not a hex number. */
 class HexNumberException implements Exception {
   HexNumberException();
 }