boolean casValue(AbstractFutureState<?> future, @Nullable Object expect, Object update) {
      return valueUpdater.compareAndSet(future, expect, update);
    }

    private static LinkageError newLinkageError(Throwable cause) {
      return new LinkageError(cause.toString(), cause);
    }

    @Override
    String atomicHelperTypeForTest() {
      return "VarHandleAtomicHelper";
    }
  }

  /**