anchor.diff:  
     final String service;
     final String title;
  -  final Widget icon;
  -  final String gaScreenName;
  -  final String gaItem;
  +  final Widget? icon;
  +  final String? gaScreenName;
  +  final String? gaItem;
   }
   
   /// Hot reload service registered by Flutter Tools.
  
positive.code: 
  class RegisteredServiceDescription {
    const RegisteredServiceDescription._({
      this.service,
      this.title,
      this.icon,
      this.gaScreenName,
      this.gaItem,
  
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/material.dart';
  
  