* invokeAll/invokeAny} throwing RejectedExecutionException, although a subset of the tasks may
   * already have been executed.
   *
   * @since 18.0 (present as MoreExecutors.sameThreadExecutor() since 10.0)
   */
  @GwtIncompatible // TODO
  public static ListeningExecutorService newDirectExecutorService() {
    return new DirectExecutorService();
  }

  /**