@Override
    public @Nullable VirtualFileEnumeration extractFileEnumeration() {
      VirtualFileEnumeration fileEnumeration1 = VirtualFileEnumeration.extract(myScope1);
      VirtualFileEnumeration fileEnumeration2 = VirtualFileEnumeration.extract(myScope2);
      if (fileEnumeration1 == null) return null;
      if (fileEnumeration2 == null) return null;
      return new IntersectionFileEnumeration(Arrays.asList(fileEnumeration1, fileEnumeration2));
    }
@Override
    public @Nullable VirtualFileEnumeration extractFileEnumeration()