anchor.diff:  // Copyright 2020 The Chromium Authors. All rights reserved.
   // Use of this source code is governed by a BSD-style license that can be
   // found in the LICENSE file.
  -
  -// @dart=2.9
   
   import 'package:flutter/material.dart' hide TextStyle;
   import 'package:flutter/widgets.dart' hide TextStyle;
  
positive.code: 
    @override
    Widget build(BuildContext context) {
      if (sizes == null) {
        return Column(
          children: [
            const SizedBox(height: denseRowSpacing),
  
negative.code:     // });
    }
  
    void _onRootChanged(TreemapNode? newRoot) {
      setState(() {
        root = newRoot;
      });
  