anchor.diff:  // 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:collection/collection.dart' show IterableExtension;
   import 'package:flutter/material.dart';
   
   import 'common_widgets.dart';
  
positive.code: }
  
  class _SnapshotScreenBodyState extends State<SnapshotScreenBody> {
    Screen _screen;
  
    @override
    void initState() {
  
negative.code:         const SizedBox(height: denseRowSpacing),
          Expanded(
            child:
                _screen != null ? _screen!.build(context) : _buildSnapshotError(),
          ),
        ],
      );
  