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

editor/tools/plugins/com.google.dart.tools.core_test/src/com/google/dart/tools/core/internal/model/testsource/FunctionTest.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.
 
 // Tests function statements and expressions.
 
 class Bug4089219 {
   int x;
   var f;
 
@@ skipping 289 matching lines @@
     int result = f(1, 2, 3);
     assert(5 == result, "expected 5 got ${result}");
   }
 
   void testFunctionDefaults1() {
     // TODO(jimhug): This return null shouldn't be necessary.
     function f() { return null; };
     (function(a = 10) { assert(a == 10); })();
     (function(a, b = 10) { assert(b == 10); })(1);
     (function(a = 10) { assert(a == null); })( f() );
-    // FAILS: (function(a = 10) { assert(a === null); })( f() );
   }
 
   void testFunctionDefaults2() {
     assert( helperFunctionDefaults2() == 10);
     assert( helperFunctionDefaults2(1) == 1);
   }
 
   void helperFunctionDefaults2(a = 10) {
     return (function(){return a;})();
   }
@@ skipping 40 matching lines @@
     foo = f;
     fooIntString = f;
 
     foo = fooIntString;
     fooIntString = foo;
 
     uf = uf2;
     uf2 = uf;
   }
 }