this.delegate = checkNotNull(delegate);
  }

  /**
   * Wraps a {@code Callable} for submission to the underlying executor. This method is also applied
   * to any {@code Runnable} passed to the default implementation of {@link #wrapTask(Runnable)}.
   */
  protected abstract <T extends @Nullable Object> Callable<T> wrapTask(Callable<T> callable);

  /**

    }

    public static boolean isNestableDeferred(@Nullable Object value) {
        return value instanceof Callable
            || isKotlinFunction0Deferrable(value);
    }

    @Nullable
    public static Object unpackNestableDeferred(@Nullable Object deferred) {
        Object current = deferred;
        while (isNestableDeferred(current)) {
            if (current instanceof Callable) {

    runConcurrentTest(
        numberOfThreads,
        new Callable<@Nullable Void>() {
          @Override
          public @Nullable Void call() throws Exception {
            long unused = ticker.read();
            return null;
          }
        });

    assertEquals(incrementByNanos * numberOfThreads, ticker.read());
  }

  /** Runs {@code callable} concurrently {@code numberOfThreads} times. */

    final SettableFuture<@Nullable Void> settableFuture = SettableFuture.create();
    ArrayList<ListenableFuture<@Nullable Void>> results = new ArrayList<>(50_001);
    results.add(
        serializer.submitAsync(
            new AsyncCallable<@Nullable Void>() {
              @Override
              public ListenableFuture<@Nullable Void> call() {
                return settableFuture;

class TrustedListenableFutureTask<V extends @Nullable Object> extends FluentFuture.TrustedFuture<V>
    implements RunnableFuture<V> {

  static <V extends @Nullable Object> TrustedListenableFutureTask<V> create(
      AsyncCallable<V> callable) {
    return new TrustedListenableFutureTask<>(callable);
  }

  static <V extends @Nullable Object> TrustedListenableFutureTask<V> create(Callable<V> callable) {

      Callable<T> callable, ListeningExecutorService listeningExecutorService) {
    checkNotNull(callable);
    checkNotNull(listeningExecutorService);
    return () -> listeningExecutorService.submit(callable);
  }

  /**
   * Wraps the given callable such that for the duration of {@link Callable#call} the thread that is
   * running will have the given name.
   *

      Callable<T> callable, ListeningExecutorService listeningExecutorService) {
    checkNotNull(callable);
    checkNotNull(listeningExecutorService);
    return () -> listeningExecutorService.submit(callable);
  }

  /**
   * Wraps the given callable such that for the duration of {@link Callable#call} the thread that is
   * running will have the given name.
   *

    final SettableFuture<@Nullable Void> settableFuture = SettableFuture.create();
    ArrayList<ListenableFuture<@Nullable Void>> results = new ArrayList<>(50_001);
    results.add(
        serializer.submitAsync(
            new AsyncCallable<@Nullable Void>() {
              @Override
              public ListenableFuture<@Nullable Void> call() {
                return settableFuture;

   */
  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override
  protected final <T extends @Nullable Object> RunnableFuture<T> newTaskFor(Callable<T> callable) {
    return TrustedListenableFutureTask.create(callable);
  }

  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override
  public ListenableFuture<?> submit(Runnable task) {
    return (ListenableFuture<?>) super.submit(task);

   */
  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override
  protected final <T extends @Nullable Object> RunnableFuture<T> newTaskFor(Callable<T> callable) {
    return TrustedListenableFutureTask.create(callable);
  }

  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override
  public ListenableFuture<?> submit(Runnable task) {
    return (ListenableFuture<?>) super.submit(task);