anchor.diff:      _navigator = null;
     }
   
  -  // The drag gesture has changed by [fractionalDelta]. The total range of the
  -  // drag should be 0.0 to 1.0.
  +  /// The drag gesture has changed by [fractionalDelta]. The total range of the
  +  /// drag should be 0.0 to 1.0.
     void dragUpdate(double fractionalDelta);
   
  -  // The drag gesture has ended with a horizontal motion of
  -  // [fractionalVelocity] as a fraction of screen width per second.
  +  /// The drag gesture has ended with a horizontal motion of
  +  /// [fractionalVelocity] as a fraction of screen width per second.
     void dragEnd(double fractionalVelocity);
   }
   
  
positive.code:       ..pushNamed(routeName);
    }
  
    static NavigatorState of(BuildContext context) {
      NavigatorState navigator = context.ancestorStateOfType(const TypeMatcher<NavigatorState>());
      assert(() {
  
negative.code:   /// The [Navigator] popped the given route.
    void didPop(Route<dynamic> route, Route<dynamic> previousRoute) { }
  
    /// The [Navigator] is being controlled by a user gesture.
    ///
    /// Used for the iOS back gesture.
    void didStartUserGesture() { }
  
    /// User gesture is no longer controlling the [Navigator].
  