anchor.diff:  /// For simple cases without additional state, consider using
   /// [AnimatedWidget].
   class AnimatedBuilder extends AnimatedWidget {
  +  /// Creates an animated builder.
  +  ///
  +  /// The [animation] argument is required.
     AnimatedBuilder({
       Key key,
       Animation<Object> animation,
  
positive.code: 
  /// Animates the position of a widget relative to its normal position.
  class SlideTransition extends AnimatedWidget {
    SlideTransition({
      Key key,
      Animation<FractionalOffset> position,
      this.transformHitTests: true,
      this.child
    }) : position = position, super(key: key, animation: position) {
      assert(position != null);
    }
  
    /// The animation that controls the position of the child.
    ///
  
negative.code: 
    @override
    Widget build(BuildContext context) {
      final double scaleValue = scale.value;
      Matrix4 transform = new Matrix4.identity()
        ..scale(scaleValue, scaleValue, 1.0);
      return new Transform(
        transform: transform,
        alignment: alignment,
  