anchor.diff:        throw UnimplementedError();
   }
   
  -class _TestingBuildStep implements BuildStep {
  -  @override
  -  final AssetId inputId;
  -
  -  @override
  -  final _TestingResolver resolver;
  -
  -  final Map<AssetId, String> assets;
  -
  -  _TestingBuildStep(this.inputId, this.assets)
  -      : resolver = _TestingResolver(assets);
  -
  -  @override
  -  Future<bool> canRead(AssetId id) async => assets.containsKey(id);
  -
  -  @override
  -  Future<String> readAsString(AssetId id, {Encoding encoding = utf8}) async =>
  -      assets[id]!;
  -
  -  @override
  -  void noSuchMethod(_) => throw UnimplementedError();
  -}
  -
  -class _TestingResolver implements Resolver {
  +class _TestingResolver implements ReleasableResolver {
     final Map<AssetId, String> assets;
     final parsedUnits = <AssetId>{};
     final resolvedLibs = <AssetId>{};
  
positive.code:       () async {
      final builder = LibraryBuilder(const _DeprecatedGenerator());
      final input = AssetId('a', 'lib/a.dart');
      final buildStep = _TestingBuildStep(input, {
        input: 'main() {}',
      });
      await builder.build(buildStep);
      expect(buildStep.resolver.parsedUnits, {input});
      expect(buildStep.resolver.resolvedLibs, isEmpty);
    });
  
    test('Searches in part files for annotations', () async {
  
negative.code: // BSD-style license that can be found in the LICENSE file.
  
  @TestOn('vm')
  import 'package:analyzer/dart/analysis/utilities.dart';
  import 'package:analyzer/dart/ast/ast.dart';
  import 'package:analyzer/dart/element/element.dart';
  