private final @Nullable ListenableFuture<? extends T>[] inputFutures;
    private volatile int delegateIndex = 0;

    private InCompletionOrderState(ListenableFuture<? extends T>[] inputFutures) {
      this.inputFutures = inputFutures;
      incompleteOutputCount = new AtomicInteger(inputFutures.length);
    }

    private void recordOutputCancellation(boolean interruptIfRunning) {