ListenableFuture<? extends V> input,
      Class<X> exceptionType,
      AsyncFunction<? super X, ? extends V> fallback,
      Executor executor) {
    AsyncCatchingFuture<V, X> output = new AsyncCatchingFuture<>(input, exceptionType, fallback);
    input.addListener(output, rejectionPropagatingExecutor(executor, output));
    return output;
  }

  /*