@Override
    public @Nullable VirtualFileEnumeration extractFileEnumeration() {
      List<VirtualFileEnumeration> fileEnumerations = new SmartList<>();
      for (GlobalSearchScope scope : myScopes) {
        VirtualFileEnumeration fileEnumeration = VirtualFileEnumeration.extract(scope);
        if (fileEnumeration == null) {
          return null;
        }
        fileEnumerations.add(fileEnumeration);
      }
      return new UnionFileEnumeration(fileEnumerations);
    }
@Override
    public @Nullable VirtualFileEnumeration extractFileEnumeration()