/*
   * These methods perform most headSet, subSet, and tailSet logic, besides parameter validation.
   */
  @SuppressWarnings("MissingOverride") // Supermethod does not exist under GWT.
  abstract ContiguousSet<C> headSetImpl(C toElement, boolean inclusive);

  @SuppressWarnings("MissingOverride") // Supermethod does not exist under GWT.
  abstract ContiguousSet<C> subSetImpl(

  /*
   * These methods perform most headSet, subSet, and tailSet logic, besides parameter validation.
   */
  @SuppressWarnings("MissingOverride") // Supermethod does not exist under GWT.
  abstract ContiguousSet<C> headSetImpl(C toElement, boolean inclusive);

  @SuppressWarnings("MissingOverride") // Supermethod does not exist under GWT.
  abstract ContiguousSet<C> subSetImpl(

  }

  /**
   * {@inheritDoc}
   *
   * @since NEXT. Note, however, that Java 19+ users can call this method with any version of Guava.
   */
  @SuppressWarnings("MissingOverride") // not an override under J2CL
  @ParametricNullness
  public V resultNow() {
    Object localValue = value();
    if (localValue == null | localValue instanceof DelegatingToFuture) {