} else if (elements instanceof EnumSet) {
      EnumSet<?> clone = ((EnumSet<?>) elements).clone();
      ImmutableSet<?> untypedResult = ImmutableEnumSet.asImmutable(clone);
      /*
       * The result has the same type argument we started with. We just couldn't express EnumSet<E>
       * or ImmutableEnumSet<E> along the way because our own <E> isn't <E extends Enum<E>>.
       *