anchor.diff:     * The error that was caused by attempting to handle the request, or `null` if
      * there was no error.
      */
  -  final Object error;
  +  final RequestError error;
   
     /**
      * A table mapping the names of result fields to their values. The table
  
positive.code:    * unknown analysis option was provided.
     */
    Response.unknownAnalysisOption(Request request, String optionName)
      : this(request.id, 'Unknown analysis option: "$optionName"');
  
    /**
     * Initialize a newly created instance to represent an error condition caused
     * by a [request] that cannot be handled by any known handlers.
     */
    Response.unknownRequest(Request request)
      : this(request.id, 'Unknown request');
  
    /**
     * Return the value of the result field with the given [name].
  
negative.code:    *       paramter_name: value
     *     }
     *   }
     *
     * where the parameters are optional and can contain any number of name/value
     * pairs.
     */
  