anchor.diff:    @override
     Map<PluginInfo, Future<plugin.Response>> broadcastRequest(
         plugin.RequestParams params,
  -      {analyzer.ContextRoot contextRoot}) {
  +      {analyzer.ContextRoot? contextRoot}) {
       broadcastedRequest = params;
       return broadcastResults ?? <PluginInfo, Future<plugin.Response>>{};
     }
  
positive.code:   }
  
    @override
    List<PluginInfo> pluginsForContextRoot(analyzer.ContextRoot contextRoot) {
      fail('Unexpected invocation of pluginsForContextRoot');
    }
  
  
negative.code: // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  import 'dart:async';
  
  import 'package:analysis_server/protocol/protocol.dart';
  import 'package:analysis_server/src/channel/channel.dart';
  import 'package:analysis_server/src/plugin/notification_manager.dart';
  import 'package:analysis_server/src/plugin/plugin_manager.dart';
  