anchor.diff:      defaultBinding("ctrl-s");
     }
   
  -  void invoke() {
  -    // TODO:
  -    spark.saveFile(null);
  -  }
  +  void invoke() => spark.saveFile(null);
   }
   
   class FileExitAction extends SparkAction {
  
positive.code:     defaultBinding("ctrl-n");
    }
  
    void invoke() {
      // TODO:
      spark.newFile(null);
    }
  }
  
  class FileOpenAction extends SparkAction {
  
negative.code:   }
  }
  
  /**
   * The abstract parent class of Spark related actions.
   */
  abstract class SparkAction extends Action {
    Spark spark;
  
  