: comparator.equals(comparator2);
    }
    return false;
  }

  // Assumes that delegate doesn't have null elements and comparator.
  static <E> ImmutableSortedSet<E> unsafeDelegateSortedSet(
      SortedSet<E> delegate, boolean isSubset) {
    return delegate.isEmpty()
        ? emptySet(delegate.comparator())
        : new RegularImmutableSortedSet<E>(delegate, isSubset);
  }