anchor.diff:  
   class Options {
     const Options({
  -    @required this.snapshot,
  -    @required this.packageConfig,
  -    @required this.forbiddenTypes,
  +    required this.snapshot,
  +    required this.packageConfig,
  +    required this.forbiddenTypes,
     });
   
     factory Options.fromArgs(List<String> args) {
  
positive.code: // Copyright 2014 The Flutter 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
  // TODO(dnfield): migrate this once vm_snapshot_analysis is migrated.
  // https://github.com/dart-lang/sdk/issues/45683
  
  import 'dart:convert';
  import 'dart:io';
  
negative.code:     packageConfigFile.readAsStringSync(),
      packageConfigFile.uri,
    );
    final Uri? packageFileUri = packageConfig.resolve(packageUri);
    final File packageFile = fs.file(packageFileUri);
    if (!packageFile.existsSync()) {
      print('File $packageFile does not exist - forbidden type has moved or been removed.');
  