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

final class Platform {
  static boolean isInstanceOfThrowableClass(Throwable t, Class<? extends Throwable> expectedClass) {
    /*
     * This method is used only by CatchingFuture, and CatchingFuture accepts only Throwable.class
     * under GWT.
     */
    return true;
  }

  static void restoreInterruptIfIsInterruptedException(Throwable t) {}

  static void interruptCurrentThread() {}