anchor.diff:  
   /// Draws a title on the [HorizontalLine]
   class HorizontalLineLabel extends FlLineLabel {
  +
     /// Resolves a label for showing.
     final String Function(HorizontalLine) labelResolver;
   
  
positive.code:     this.bar,
      this.barIndex,
      FlSpot spot,
    )   : spotIndex = bar.spots.indexOf(spot),
          super(spot.x, spot.y);
  }
  
  /// Holds data of showing each row item in the tooltip popup.
  class LineTooltipItem {
    /// Showing text.
    final String text;
  
  
negative.code:   /// Lerps a [LineChartData] based on [t] value, check [Tween.lerp].
    @override
    LineChartData lerp(double t) => begin.lerp(begin, end, t);
  }