anchor.diff:  import 'package:analyzer/dart/analysis/analysis_context.dart';
   import 'package:analyzer/dart/analysis/results.dart';
   import 'package:analyzer/dart/analysis/session.dart';
  -import 'package:analyzer/dart/element/element.dart';
  -import 'package:analyzer/dart/element/visitor.dart';
   import 'package:analyzer/file_system/file_system.dart';
   import 'package:analyzer/src/dart/analysis/analysis_context_collection.dart';
   import 'package:analyzer/src/dart/analysis/byte_store.dart';
  
positive.code:     verifyCreatedCollection();
    }
  }
  
  /// Wraps the given [_ElementVisitorFunction] into an instance of
  /// [engine.GeneralizingElementVisitor].
  class _ElementVisitorFunctionWrapper extends GeneralizingElementVisitor<void> {
    final _ElementVisitorFunction function;
    _ElementVisitorFunctionWrapper(this.function);
  
    @override
    void visitElement(Element element) {
      function(element);
      super.visitElement(element);
    }
  }
  
negative.code: 
  import 'src/utilities/mock_packages.dart';
  
  class AbstractContextTest with ResourceProviderMixin {
    static bool _lintRulesAreRegistered = false;
  
  