@Override
  final void addInitialException(Set<Throwable> seen) {
    checkNotNull(seen);
    if (!isCancelled()) {
      /*
       * requireNonNull is safe because:
       *
       * - This is a TrustedFuture, so tryInternalFastPathGetFailure will in fact return the failure
       *   cause if this Future has failed.
       *
       * - And this future *has* failed: This method is called only from handleException (through

  /**
   * A less abstract subclass of AbstractFuture. This can be used to optimize setFuture by ensuring
   * that {@link #get} calls exactly the implementation of {@link AbstractFuture#get}.
   */
  abstract static class TrustedFuture<V extends @Nullable Object> extends FluentFuture<V>
      implements AbstractFuture.Trusted<V> {
    @CanIgnoreReturnValue
    @Override
    @ParametricNullness

        return scheduledDelegate.compareTo(other);
      }
    }

    @GwtIncompatible // TODO
    private static final class NeverSuccessfulListenableFutureTask
        extends AbstractFuture.TrustedFuture<@Nullable Void> implements Runnable {
      private final Runnable delegate;

      NeverSuccessfulListenableFutureTask(Runnable delegate) {
        this.delegate = checkNotNull(delegate);
      }