@CanIgnoreReturnValue
    Builder<C> combine(Builder<C> builder) {
      addAll(builder.ranges);
      return this;
    }

    /**
     * Returns an {@code ImmutableRangeSet} containing the ranges added to this builder.
     *
     * @throws IllegalArgumentException if any input ranges have nonempty overlap
     */
    public ImmutableRangeSet<C> build() {
      ImmutableList.Builder<Range<C>> mergedRangesBuilder =