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

utils/pub/yaml/yaml_map.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.
 
 /**
  * This class wraps behaves almost identically to the normal Dart Map
  * implementation, with the following differences:
  *
  * * It allows null, NaN, boolean, list, and map keys.
  * * It defines `==` structurally. That is, `yamlMap1 == yamlMap2` if they have
@@ skipping 67 matching lines @@
   }
 }
 
 /**
  * Returns the hash code for [obj]. This includes null, true, false, maps, and
  * lists. Also handles self-referential structures.
  */
 int _hashCode(obj, [List parents]) {
   if (parents == null) {
     parents = [];
-  } else if (parents.some((p) => p === obj)) {
+  } else if (parents.some((p) => identical(p, obj))) {
     return -1;
   }
 
   parents.add(obj);
   try {
     if (obj == null) return 0;
     if (obj == true) return 1;
     if (obj == false) return 2;
     if (obj is Map) {
       return _hashCode(obj.keys, parents) ^
         _hashCode(obj.values, parents);
     }
     if (obj is List) {
       // This is probably a really bad hash function, but presumably we'll get this
       // in the standard library before it actually matters.
       int hash = 0;
       for (var e in obj) {
         hash ^= _hashCode(e, parents);
       }
       return hash;
     }
     return obj.hashCode;
   } finally {
     parents.removeLast();
   }
 }