anchor.diff:    void _arcTo(double left, double top, double right, double bottom,
                 double startAngle, double sweepAngle, bool forceMoveTo) native "Path_arcTo";
   
  -  /// Appends up to four conic curves weighted to describe an oval of [radius]
  -  /// and rotated by [rotation].
  +  /// Appends up to four conic curves weighted to describe an oval of `radius`
  +  /// and rotated by `rotation`.
     ///
     /// The first curve begins from the last point in the path and the last ends
  -  /// at [arcEnd]. The curves follow a path in a direction determined by
  -  /// [clockwise] and [largeArc] in such a way that the sweep angle
  +  /// at `arcEnd`. The curves follow a path in a direction determined by
  +  /// `clockwise` and `largeArc` in such a way that the sweep angle
     /// is always less than 360 degrees.
     ///
     /// A simple line is appended if either either radii are zero or the last
  -  /// point in the path is [arcEnd]. The radii are scaled to fit the last path
  +  /// point in the path is `arcEnd`. The radii are scaled to fit the last path
     /// point if both are greater than zero but too small to describe an arc.
     ///
     void arcToPoint(Offset arcEnd, {
  
positive.code:   /// that intersects the center of the rectangle and with positive
    /// angles going clockwise around the oval.
    ///
    /// The line segment added if [forceMoveTo] is false starts at the
    /// current point and ends at the start of the arc.
    void arcTo(Rect rect, double startAngle, double sweepAngle, bool forceMoveTo) {
      assert(_rectIsValid(rect));
  
negative.code:   ///
    ///  * [save], which saves the current state, but does not create a new layer
    ///    for subsequent commands.
    ///  * [BlendMode], which discusses the use of [Paint.blendMode] with
    ///    [saveLayer].
    void saveLayer(Rect bounds, Paint paint) {
      assert(_rectIsValid(bounds));
      assert(paint != null);
  