anchor.diff:        Transition transition = new Transition(
           key: new Key.fromObjectIdentity(historyEntry),
           content: content,
  -        direction: (i <= state.historyIndex) ? TransitionDirection.forward : TransitionDirection.reverse,
  +        direction: (i <= state.historyIndex) ? Direction.forward : Direction.reverse,
           interactive: (i == state.historyIndex),
           onDismissed: () {
             setState(() {
  
positive.code: // and support multiple transition types
  const Duration _kTransitionDuration = const Duration(milliseconds: 150);
  const Point _kTransitionStartPoint = const Point(0.0, 75.0);
  enum TransitionDirection { forward, reverse }
  class Transition extends AnimatedComponent {
    Transition({
      Key key,
  
negative.code:     this.interactive
    }): super(key: key);
    Widget content;
    Direction direction;
    bool interactive;
    Function onDismissed;
    Function onCompleted;
  