}

  /** Unboxes {@code obj}. Assumes that obj is not {@code null} or a {@link SetFuture}. */
  @ParametricNullness
  private V getDoneValue(Object obj) throws ExecutionException {
    // While this seems like it might be too branch-y, simple benchmarking proves it to be
    // unmeasurable (comparing done AbstractFutures with immediateFuture)
    if (obj instanceof Cancellation) {

   */
  @GwtIncompatible // java.time.Duration
  @SuppressWarnings("GoodTime") // duration decomposition
  private static long toNanosSaturated(java.time.Duration duration) {
    // Using a try/catch seems lazy, but the catch block will rarely get invoked (except for
    // durations longer than approximately +/- 292 years).
    try {
      return duration.toNanos();
    } catch (ArithmeticException tooBig) {

                fileSize = response.getDataSize();

                // this is so damn unreliable, needs another race-prone query if required
                haveAttributes = false;

                // This seems to be the only way to obtain a reliable (with respect to locking) file size here
                // It is more critical than other attributes because append mode depends on it.