anchor.diff:    String? _content;
     String? _contentHash;
     LineInfo? _lineInfo;
  -  Set<String>? _definedClassMemberNames;
  -  Set<String>? _definedTopLevelNames;
  -  Set<String>? _referencedNames;
     Uint8List? _unlinkedSignature;
     String? _unlinkedKey;
     String? _informativeKey;
  
positive.code:   /// Invalidate any data that depends on the current unlinked data of the file,
    /// because [refresh] is going to recompute the unlinked data.
    void _invalidateCurrentUnresolvedData() {
      // Invalidate unlinked information.
      _definedTopLevelNames = null;
      _definedClassMemberNames = null;
      _referencedNames = null;
  
      if (_driverUnlinkedUnit != null) {
        for (var name in _driverUnlinkedUnit!.subtypedNames) {
          var files = _fsState._subtypedNameToFiles[name];
  
negative.code: 
    /// The class member names defined by the file.
    Set<String> get definedClassMemberNames {
      return _driverUnlinkedUnit!.definedClassMemberNames;
    }
  
    /// The top-level names defined by the file.
    Set<String> get definedTopLevelNames {
      return _driverUnlinkedUnit!.definedTopLevelNames;
    }
  
    /// Return the set of all directly referenced files - imported, exported or
  