abstract @Nullable Waiter gasWaiters(AbstractFutureState<?> future, Waiter update);

    /** Performs a GAS operation on {@link AbstractFutureState#listenersField}. */
    abstract @Nullable Listener gasListeners(AbstractFutureState<?> future, Listener update);

    /** Performs a CAS operation on {@link AbstractFutureState#valueField}. */
    abstract boolean casValue(

    abstract @Nullable Waiter gasWaiters(AbstractFutureState<?> future, Waiter update);

    /** Performs a GAS operation on {@link AbstractFutureState#listenersField}. */
    abstract @Nullable Listener gasListeners(AbstractFutureState<?> future, Listener update);

    /** Performs a CAS operation on {@link AbstractFutureState#valueField}. */
    abstract boolean casValue(

    extends AbstractFuture.TrustedFuture<OutputT> {
  /*
   * The following fields are package-private, even though we intend never to use them outside this
   * file. For discussion, see AbstractFutureState.
   */

  // Lazily initialized the first time we see an exception; not released until all the input futures
  // have completed and we have processed them all.