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

utils/peg/pegparser.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.
 
 library Peg Parser;
 
 /*
  * The following functions are combinators for building Rules.
  *
  * A rule is one of the following
@@ skipping 763 matching lines @@
   // A map from position to result.  Can this be replaced with something
   // smaller?
   // TODO: figure out how to discard the map and parseInstance after parsing.
   Map<int,Object> map;
 
   _MemoRule(this._rule);
 
   _match(state, pos) {
     // See if we are still parsing the same input.  Relies on the fact that the
     // input is a string and strings are immutable.
-    if (parseInstance !== state._text) {
+    if (!identical(parseInstance, state._text)) {
       map = new Map<int,Object>();
       parseInstance = state._text;
     }
     // TODO: does this have to check or preserve parse state (like
     // inWhitespaceMode, error position info etc?)
     // Stored result can be null (memoized failure).
     if (map.containsKey(pos)) {
       return map[pos];
     }
     var match = _rule.match(state, pos);
@@ skipping 54 matching lines @@
   add(s);
   add(t);
   add(u);
   add(v);
   add(w);
   add(x);
   add(y);
   add(z);
   return list;
 }