anchor.diff:  // 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';
  
positive.code: 
  class Options {
    const Options({
      @required this.snapshot,
      @required this.packageConfig,
      @required this.forbiddenTypes,
    });
  
    factory Options.fromArgs(List<String> args) {
  
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.');
  