anchor.diff:    /// The route name will be passed to that navigator's [onGenerateRoute]
     /// callback. The returned route will be pushed into the navigator.
     ///
  -  /// Returns a Future that completes when the pushed route is popped.
  +  /// Returns a [Future] that completes to the `result` value passed to [pop]
  +  /// when the pushed route is popped off the navigator.
     ///
     /// Typical usage is as follows:
     ///
  
positive.code:     return Navigator.of(context).pushNamed(routeName);
    }
  
    /// Push a route onto the navigator that most tightly encloses the given context.
    ///
    /// Adds the given route to the Navigator's history, and transitions to it.
    /// The route will have didPush() and didChangeNext() called on it; the
    /// previous route, if any, will have didChangeNext() called on it; and the
    /// Navigator observer, if any, will have didPush() called on it.
    ///
    /// Returns a Future that completes when the pushed route is popped.
    static Future<dynamic> push(BuildContext context, Route<dynamic> route) {
      return Navigator.of(context).push(route);
    }
  
negative.code:   /// Ongoing gestures within the current route are canceled when a new route is
    /// pushed.
    ///
    /// Returns a [Future] that completes to the `result` value passed to [pop]
    /// when the pushed route is popped off the navigator.
    Future<dynamic> push(Route<dynamic> route) {
      assert(!_debugLocked);
      assert(() { _debugLocked = true; return true; });
  