if (set.isEmpty()) {
        /*
         * The (tooLow + 1, tooHigh) arguments below would be invalid because tooLow would be
         * greater than tooHigh.
         */
        return ContiguousSet.create(Range.openClosed(0, 1), DiscreteDomain.integers()).subSet(0, 1);
      }
      int tooHigh = set.last() + 1;
      int tooLow = set.first() - 1;
      set.add(tooHigh);
      set.add(tooLow);

  }

  boolean isEmpty() {
    // The casts are safe because of the has*Bound() checks.
    return (hasUpperBound() && tooLow(uncheckedCastNullableTToT(getUpperEndpoint())))
        || (hasLowerBound() && tooHigh(uncheckedCastNullableTToT(getLowerEndpoint())));
  }

  boolean tooLow(@ParametricNullness T t) {
    if (!hasLowerBound()) {
      return false;
    }

  }

  boolean isEmpty() {
    // The casts are safe because of the has*Bound() checks.
    return (hasUpperBound() && tooLow(uncheckedCastNullableTToT(getUpperEndpoint())))
        || (hasLowerBound() && tooHigh(uncheckedCastNullableTToT(getLowerEndpoint())));
  }

  boolean tooLow(@ParametricNullness T t) {
    if (!hasLowerBound()) {
      return false;
    }

      @Nullable Entry<E> prevEntry;

      @Override
      public boolean hasNext() {
        if (current == null) {
          return false;
        } else if (range.tooHigh(current.getElement())) {
          current = null;
          return false;
        } else {
          return true;
        }
      }

      @Override
      public Entry<E> next() {

      @Nullable Entry<E> prevEntry;

      @Override
      public boolean hasNext() {
        if (current == null) {
          return false;
        } else if (range.tooHigh(current.getElement())) {
          current = null;
          return false;
        } else {
          return true;
        }
      }

      @Override
      public Entry<E> next() {