@ElementTypesAreNonnullByDefault
abstract class AggregateFutureState<OutputT extends @Nullable Object>
    extends AbstractFuture.TrustedFuture<OutputT> {
  // Lazily initialized the first time we see an exception; not released until all the input futures
  // have completed and we have processed them all.
  @CheckForNull private volatile Set<Throwable> seenExceptions = null;

  private volatile int remaining;

  private static final AtomicHelper ATOMIC_HELPER;

@ElementTypesAreNonnullByDefault
abstract class AggregateFutureState<OutputT extends @Nullable Object>
    extends AbstractFuture.TrustedFuture<OutputT> {
  // Lazily initialized the first time we see an exception; not released until all the input futures
  // & this future completes. Released when the future releases the reference to the running state
  private @Nullable Set<Throwable> seenExceptions = null;
  private int remaining;