anchor.diff:  /// This is a ListView of text lines, with a monospace font and a border.
   class _ConsoleOutput extends StatefulWidget {
     const _ConsoleOutput({
  -    Key key,
  -    @required this.lines,
  +    Key? key,
  +    required this.lines,
       this.footer,
     }) : super(key: key);
   
     final ValueListenable<List<ConsoleLine>> lines;
   
  -  final Widget footer;
  +  final Widget? footer;
   
     @override
     _ConsoleOutputState createState() => _ConsoleOutputState();
  
positive.code:   }
  
    void _onConsoleLinesChanged() {
      final nextLines = widget.lines.value ?? const [];
      if (nextLines == _currentLines) return;
  
      var forceScrollIntoView = false;
  
negative.code: // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // ignore_for_file: import_of_legacy_library_into_null_safe
  
  import 'package:flutter/foundation.dart';
  import 'package:flutter/material.dart';
  