* SetView}.
     */
    abstract int minSize();

    /**
     * Returns the {@link #minSize()} of {@code set} if it is a {@link SetView}, or the exact {@link
     * #size()} of {@code set} otherwise.
     */
    static int minSize(Set<?> set) {
      return set instanceof SetView ? ((SetView<?>) set).minSize() : set.size();
    }

    /**

  }

  /**
   * Returns a {@link SetView} with a {@link SetView#minSize()} of {@code min} and a {@link
   * SetView#maxSize()} of {@code max}.
   */
  private static SetView<Integer> setSizeRange(int min, int max) {
    checkArgument(min >= 0 && max >= min);
    SetView<Integer> set = difference(setSize(max), setSize(max - min));
    checkState(set.minSize() == min && set.maxSize() == max);
    return set;
  }

  /**

  }

  private static final class PaddedLock extends ReentrantLock {
    /*
     * Padding from 40 into 64 bytes, same size as cache line. Might be beneficial to add a fourth
     * long here, to minimize chance of interference between consecutive locks, but I couldn't
     * observe any benefit from that.
     */
    long unused1;
    long unused2;
    long unused3;

    PaddedLock() {
      super(false);

  // The suppression also covers the cast to E[], discussed below.
  // In the backport, we don't have those cases and thus don't need this suppression.
  // We keep it to minimize diffs.
  @SuppressWarnings("unchecked")
  public static <E> ImmutableSet<E> copyOf(Collection<? extends E> elements) {
    /*
     * TODO(lowasser): consider checking for ImmutableAsList here

    // * The element with (index == from) should be kept.
    // * Everything with (index > from) has not been checked yet.

    // Check from the end of the list backwards (minimize expected cost of
    // moving elements when remove() is called). Stop before 'from' because
    // we already know that should be kept.
    for (int n = list.size() - 1; n > from; n--) {

     * ImmutableSortedSet#orderedBy}.
     */
    /*
     * TODO(cpovirk): use Object[] instead of E[] in the mainline? (The backport is different and
     * doesn't need this suppression, but we keep it to minimize diffs.) Generally be more clear
     * about when we have an Object[] vs. a Comparable[] or other array type in internalArray? If we
     * used Object[], we might be able to optimize toArray() to use clone() sometimes. (See