// Pretend the comparator can compare anything. If it turns out it can't
    // compare a and b, we should get a CCE or NPE on the subsequent line. Only methods
    // that are spec'd to throw CCE and NPE should call this.
    @SuppressWarnings({"unchecked", "nullness"})
    Comparator<@Nullable Object> unsafeComparator = (Comparator<@Nullable Object>) comparator;
    return unsafeComparator.compare(a, b);

    checkNotNull(domain);
    if (isEmpty()) {
      return ImmutableSortedSet.of();
    }
    Range<C> span = span().canonical(domain);
    if (!span.hasLowerBound()) {
      // according to the spec of canonical, neither this ImmutableRangeSet nor
      // the range have a lower bound
      throw new IllegalArgumentException(
          "Neither the DiscreteDomain nor this range set are bounded below");

   * Object#equals(Object)}" as defined by {@link Comparator}. Use caution when building a {@link
   * SortedSet} or {@link SortedMap} from it, as the resulting collection will not behave exactly
   * according to spec.
   *
   * <p>This ordering is not serializable, as its implementation relies on {@link
   * System#identityHashCode(Object)}, so its behavior cannot be preserved across serialization.
   *
   * @since 2.0
   */

     *
     * @return a reference to {@code set}, for convenience
     */
    // Note: S should logically extend Set<? super E> but can't due to either
    // some javac bug or some weirdness in the spec, not sure which.
    @CanIgnoreReturnValue
    public <S extends Set<E>> S copyInto(S set) {
      set.addAll(this);
      return set;
    }

    /**

  /**
   * The HTTP <a href="http://html.spec.whatwg.org/multipage/semantics.html#hyperlink-auditing">
   * {@code Ping-From}</a> header field name.
   *
   * @since 19.0
   */
  public static final String PING_FROM = "Ping-From";
  /**
   * The HTTP <a href="http://html.spec.whatwg.org/multipage/semantics.html#hyperlink-auditing">
   * {@code Ping-To}</a> header field name.