return e;
  }

  // catchingAsync tests cloned from the old withFallback tests:

  public void testCatchingAsync_inputDoesNotRaiseException() throws Exception {
    AsyncFunction<Throwable, Integer> fallback = unexpectedAsyncFunction();
    ListenableFuture<Integer> originalFuture = immediateFuture(7);
    ListenableFuture<Integer> faultTolerantFuture =

    return (FluentFuture<V>) Futures.catching(this, exceptionType, fallback, executor);
  }

  public final FluentFuture<V> catchingAsync(
      Class<Throwable> exceptionType,
      AsyncFunction<? super Throwable, ? extends V> fallback,
      Executor executor) {
    return (FluentFuture<V>) Futures.catchingAsync(this, exceptionType, fallback, executor);
  }

    return e;
  }

  // catchingAsync tests cloned from the old withFallback tests:

  public void testCatchingAsync_inputDoesNotRaiseException() throws Exception {
    AsyncFunction<Throwable, Integer> fallback = unexpectedAsyncFunction();
    ListenableFuture<Integer> originalFuture = immediateFuture(7);
    ListenableFuture<Integer> faultTolerantFuture =

    extends AbstractFuture<V> {
  /*
   * This server copy of the class is empty. The corresponding GWT copy contains alternative
   * versions of catching() and catchingAsync() with slightly different signatures from the ones
   * found in FluentFuture.java.
   */

  @Partially.GwtIncompatible("AVAILABLE but requires exceptionType to be Throwable.class")
  public final <X extends Throwable> FluentFuture<V> catchingAsync(
      Class<X> exceptionType, AsyncFunction<? super X, ? extends V> fallback, Executor executor) {
    return (FluentFuture<V>) Futures.catchingAsync(this, exceptionType, fallback, executor);
  }

  /**
   * Returns a future that delegates to this future but will finish early (via a {@link

@ElementTypesAreNonnullByDefault
abstract class GwtFuturesCatchingSpecialization {
  /*
   * This server copy of the class is empty. The corresponding GWT copy contains alternative
   * versions of catching() and catchingAsync() with slightly different signatures from the ones
   * found in Futures.java.
   */

      Executor executor) {
    return AbstractCatchingFuture.create(input, exceptionType, fallback, executor);
  }

  public static <V extends @Nullable Object> ListenableFuture<V> catchingAsync(
      ListenableFuture<? extends V> input,
      Class<Throwable> exceptionType,
      AsyncFunction<? super Throwable, ? extends V> fallback,
      Executor executor) {

  }

  public void testCatchingAsync() throws Exception {
    FluentFuture<?> f =
        FluentFuture.from(immediateFailedFuture(new CustomRuntimeException()))
            .catchingAsync(
                Throwable.class,
                new AsyncFunction<Throwable, Class<?>>() {
                  @Override
                  public ListenableFuture<Class<?>> apply(Throwable input) {

  }

  public void testCatchingAsync() throws Exception {
    FluentFuture<?> f =
        FluentFuture.from(immediateFailedFuture(new CustomRuntimeException()))
            .catchingAsync(
                Throwable.class,
                new AsyncFunction<Throwable, Class<?>>() {
                  @Override
                  public ListenableFuture<Class<?>> apply(Throwable input) {

          @Override
          public String toString() {
            return fallback.toString();
          }
        };
    // TODO(dpb): Switch to future.catchingSync when that exists (passing a throwing function).
    return derive(future.catchingAsync(exceptionType, applyFallback, executor));
  }

  /**
   * Returns a new {@code ClosingFuture} pipeline step derived from this one by applying a function