anchor.diff:   */
   @proxy
   class JsonObject<E> extends Object implements Map, Iterable  {
  -  /// The original JSON string
  -  var _jsonString;
  -
     /// Contains either a [List] or [Map]
     var _objectData;
     
  
positive.code:    * rather than a json string.
     */
    JsonObject.fromMap(Map map) {
      _jsonString = encoder.convert(map);
      _objectData = map;
      _extractElements(_objectData);
      isExtendable = false;
    }
  
    static JsonObject toTypedJsonObject(JsonObject src, JsonObject dest) {
      dest._jsonString = src._jsonString;
      dest._objectData = src._objectData;
      dest.isExtendable = false;
      return dest;
  
negative.code:     if (t == null) {
        t = new JsonObject();
      }
      t._objectData = decoder.convert(_jsonString);
      t._extractElements(t._objectData);
      t.isExtendable = false;
      return t;
  