anchor.diff:          getFunctionReferences =
               UnmodifiableBidirectionalMapView(getFunctionReferences),
           globalDeclarations = UnmodifiableSetView(globalDeclarations),
  -        sources = UnmodifiableMapView(sources),
  -        importers = UnmodifiableMapView(importers);
  +        sources = UnmodifiableMapView(sources);
   
     /// Constructs a new [References] object based on a [stylesheet] (imported by
     /// [importer]) and its dependencies.
  
positive.code: import '../../util/bidirectional_map.dart';
  import '../../util/unmodifiable_bidirectional_map_view.dart';
  import '../../utils.dart';
  import 'built_in_functions.dart';
  import 'member_declaration.dart';
  import 'reference_source.dart';
  import 'scope.dart';
  
  
negative.code:   References build(Stylesheet stylesheet, Importer importer) {
      _importer = importer;
      _scope = Scope();
      _moduleScopes[stylesheet.span.sourceUrl] = _scope;
      _declarationSources = {};
      _moduleSources[stylesheet.span.sourceUrl] = _declarationSources;
  