anchor.diff:     *
      * Throws [FormatException] if the input is not valid JSON text.
      */
  -  Object convert(String input) => _parseJson(input, _reviver);
  +  dynamic convert(String input) => _parseJson(input, _reviver);
   
     /**
      * Starts a conversion from a chunked JSON string to its corresponding
  
positive.code:    *
     * The default [reviver] (when not provided) is the identity function.
     */
    Object decode(String source, {reviver(var key, var value)}) {
      if (reviver == null) return decoder.convert(source);
      return new JsonDecoder(reviver).convert(source);
    }
  
negative.code:    * If [toEncodable] is omitted, it defaults to calling `.toJson()` on the
     * unencodable object.
     */
    String encode(Object value, {toEncodable(var object)}) {
      if (toEncodable == null) return encoder.convert(value);
      return new JsonEncoder(toEncodable).convert(value);
    }
  