anchor.diff:    void next([callback()]);
   
     ///Interrupt this chain. If [statusCode] or [responseValue] is provided,
  -  ///a new Response will be created. 
  +  ///a new Response will be created.
     void interrupt({int statusCode, Object responseValue, String responseType});
  -  
  +
     ///Returns true if this chain was interrupted
     bool get interrupted;
   
  
positive.code:     });
  
    });
    
  }
  
  /**
   * Handle a [HttpRequest].
   * 
   * Be sure to call [setUp] before handling requests
   * with this method.
   */
  
negative.code: 
  /**
   * An error response.
   *
   * If a route returns or throws an [ErrorResponse], then
   * the framework will serialize [error], and create a
   * response with status [statusCode].
   *
   */
  class ErrorResponse {
  
    final int statusCode;
    final Object error;
  
    ErrorResponse(this.statusCode, this.error);
  
  }
  
  /**
   * User credentials from request
   *
   */
  class Credentials {
  
    String username;
    String password;
  
    Credentials(this.username, this.password);
  
  }
  