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

utils/pub/yaml/deep_equals.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 deep_equals;
 
 /**
  * Returns whether two objects are structurally equivalent. This considers NaN
  * values to be equivalent. It also handles self-referential structures.
  */
 bool deepEquals(obj1, obj2, [List parents1, List parents2]) {
-  if (obj1 === obj2) return true;
+  if (identical(obj1, obj2)) return true;
   if (parents1 == null) {
     parents1 = [];
     parents2 = [];
   }
 
   // parents1 and parents2 are guaranteed to be the same size.
   for (var i = 0; i < parents1.length; i++) {
-    var loop1 = obj1 === parents1[i];
-    var loop2 = obj2 === parents2[i];
+    var loop1 = identical(obj1, parents1[i]);
+    var loop2 = identical(obj2, parents2[i]);
     // If both structures loop in the same place, they're equal at that point in
     // the structure. If one loops and the other doesn't, they're not equal.
     if (loop1 && loop2) return true;
     if (loop1 || loop2) return false;
   }
 
   parents1.add(obj1);
   parents2.add(obj2);
   try {
     if (obj1 is List && obj2 is List) {
@@ skipping 35 matching lines @@
 }
 
 /**
  * Returns whether two doubles are equivalent. This differs from `d1 == d2` in
  * that it considers NaN to be equal to itself.
  */
 bool _doubleEquals(double d1, double d2) {
   if (d1.isNaN && d2.isNaN) return true;
   return d1 == d2;
 }