* on the fields of TimeoutFuture. This field is slightly different from the fields discussed
   * there: cancel() never reads this field, only writes to it. That makes the race here completely
   * harmless, rather than just 99.99% harmless.
   */
  @CheckForNull @LazyInit private List<@Nullable Present<V>> values;

  CollectionFuture(

      super(message);
    }

    @Override
    public synchronized Throwable fillInStackTrace() {
      setStackTrace(new StackTraceElement[0]);
      return this; // no stack trace, wouldn't be useful anyway
    }
  }

  @Override
  @CheckForNull
  protected String pendingToString() {
    ListenableFuture<? extends V> localInputFuture = delegateRef;

    /*
     * The initialization of seenExceptions has to be more complicated than we'd like. The simple
     * approach would be for each caller CAS it from null to a Set populated with its exception. But
     * there's another race: If the first thread fails with an exception and a second thread
     * immediately fails with the same exception:
     *
     * Thread1: calls setException(), which returns true, context switch before it can CAS