anchor.diff:        BidirectionalMap<FunctionExpression, MemberDeclaration<FunctionRule>>();
     final _globalDeclarations = <MemberDeclaration>{};
     final _sources = <SassNode, ReferenceSource>{};
  -  final _importers = <Uri, Importer>{};
   
     /// The current global scope.
     ///
  
positive.code: 
      var stylesheet = result.item2;
      var canonicalUrl = stylesheet.span.sourceUrl;
      if (_moduleScopes.containsKey(canonicalUrl)) return canonicalUrl;
  
      var oldScope = _scope;
      _scope = Scope();
      _moduleScopes[canonicalUrl] = _scope;
      var oldSources = _declarationSources;
      _declarationSources = {};
      _importers[canonicalUrl] = result.item1;
      _moduleSources[canonicalUrl] = _declarationSources;
      var oldImporter = _importer;
      _importer = result.item1;
      visitStylesheet(stylesheet);
      _checkUnresolvedReferences(_scope);
      _importer = oldImporter;
      _scope = oldScope;
      _declarationSources = oldSources;
      return canonicalUrl;
    }
  
  
negative.code: import '../../util/bidirectional_map.dart';
  import '../../util/unmodifiable_bidirectional_map_view.dart';
  import '../../utils.dart';
  import 'member_declaration.dart';
  import 'scope.dart';
  
  import 'built_in_functions.dart';
  import 'reference_source.dart';
  import 'scope.dart';
  
  import 'built_in_functions.dart';
  import 'reference_source.dart';
  import 'scope.dart';
  
  