}
          // Note: The only way this CAS could fail is if cancel() has raced with us. That is ok.
          boolean unused = ATOMIC_HELPER.casValue(this, valueToSet, failure);
        }
        return true;
      }
      localValue = value; // we lost the cas, fall through and maybe cancel
    }
    // The future has already been set to something. If it is cancellation we should cancel the
    // incoming future.

      } else {
        builder.append("PENDING");
      }
    }
    return builder.append("]").toString();
  }

  /**
   * Provide a human-readable explanation of why this future has not yet completed.
   *
   * @return null if an explanation cannot be provided because the future is done.
   */
  @Nullable
  String pendingToString() {
    if (state == State.DELEGATED) {