@Override
  public @NotNull MultiHostRegistrar startInjecting(@NotNull Language language, @Nullable String extension) {
    fileExtension = extension;
    placeInfos = new SmartList<>();

    if (!cleared) {
      clear();
      throw new IllegalStateException("Seems you haven't called doneInjecting()");
    }
    currentThread = Thread.currentThread();

    if (LanguageParserDefinitions.INSTANCE.forLanguage(language) == null) {
      throw new UnsupportedOperationException("Cannot inject language '" + language + "' because it has no ParserDefinition");
    }
    myLanguage = language;
    return this;
  }
@Override
  public @NotNull MultiHostRegistrar startInjecting(@NotNull Language language, @Nullable String extension)