anchor.diff:    }
   
     Text buildNameAndSizeText({
  -    @required Color textColor,
  -    @required bool oneLine,
  +    required Color? textColor,
  +    required bool oneLine,
     }) {
       return Text(
  -      widget.rootNode.displayText(oneLine: oneLine),
  +      widget.rootNode!.displayText(oneLine: oneLine),
         style: TextStyle(color: textColor),
         textAlign: TextAlign.center,
         overflow: TextOverflow.ellipsis,
  
positive.code: 
  class PositionedCell extends Positioned {
    PositionedCell({
      @required this.rect,
      @required this.node,
      @required child,
    }) : super(
            left: rect.left,
            top: rect.top,
  
negative.code: 
    final double height;
  
    final void Function(TreemapNode? node) onRootChangedCallback;
  
    static const PivotType pivotType = PivotType.pivotByMiddle;
  
  