&& isHashCodeFast()
        && ((ImmutableSet<?>) object).isHashCodeFast()
        && hashCode() != object.hashCode()) {
      return false;
    }
    return Sets.equalsImpl(this, object);
  }

  @Override
  public int hashCode() {
    return Sets.hashCodeImpl(this);
  }

  // This declaration is needed to make Set.iterator() and
  // ImmutableCollection.iterator() consistent.
  @Override