* dummy version.
   *
   * @throws UnsupportedOperationException always
   * @deprecated <b>Pass a parameter of type {@code Comparable} to use {@link
   *     ImmutableSortedSet#of(Comparable)}.</b>
   */
  @DoNotCall("Pass a parameter of type Comparable")
  @Deprecated
  public static <E> ImmutableSortedSet<E> of(E element) {
    throw new UnsupportedOperationException();
  }

    assertEquals(
        "Shouldn't catch any more events when unregistered.", expectedEvents, catcher2.getEvents());
  }

  // NOTE: This test will always pass if register() is thread-safe but may also
  // pass if it isn't, though this is unlikely.
  public void testRegisterThreadSafety() throws Exception {
    List<StringCatcher> catchers = Lists.newCopyOnWriteArrayList();

    assertEquals(
        "Shouldn't catch any more events when unregistered.", expectedEvents, catcher2.getEvents());
  }

  // NOTE: This test will always pass if register() is thread-safe but may also
  // pass if it isn't, though this is unlikely.
  public void testRegisterThreadSafety() throws Exception {
    List<StringCatcher> catchers = Lists.newCopyOnWriteArrayList();

     *
     * <p>This method is used when testing iterators without a known ordering. We poll the target
     * iterator's next element and pass it to the reference iterator through this method so it can
     * return the same element. This enables the assertion to pass and the reference iterator to
     * properly update its state.
     */
    void promoteToNext(E e) {
      if (nextElements.remove(e)) {

  private enum SupplierFunctionImpl implements SupplierFunction<@Nullable Object> {
    INSTANCE;

    // Note: This makes T a "pass-through type"
    @Override
    @CheckForNull
    public Object apply(Supplier<@Nullable Object> input) {
      return input.get();
    }

    @Override
    public String toString() {

   * single-threaded.
   */
  @GwtIncompatible // GWT is single threaded
  public void testCopyOf_threadSafe() {
    /*
     * The actual collections that we pass as inputs will be wrappers around these, so
     * ImmutableSet.copyOf won't short-circuit because it won't see an ImmutableSet input.
     */
    ImmutableList<ImmutableSet<String>> distinctCandidatesByAscendingSize =

   * single-threaded.
   */
  @GwtIncompatible // GWT is single threaded
  public void testCopyOf_threadSafe() {
    /*
     * The actual collections that we pass as inputs will be wrappers around these, so
     * ImmutableSet.copyOf won't short-circuit because it won't see an ImmutableSet input.
     */
    ImmutableList<ImmutableSet<String>> distinctCandidatesByAscendingSize =

     * actually reading from the fields in any case in which they might be null (as proven by the
     * requireNonNull checks below). Plus, we're *already* lying here, since newHeader passes a null
     * key and value, which we pass to the superconstructor, even though the key and value type for
     * a given entry might not include null. The right fix for the header problems is probably to

  // - @PolyNull means "@Nullable or @Nonnull"
  //   (That would be unsound for an input Iterable<@Nullable Foo>. So, if we wanted to use
  //   @PolyNull, we would have to restrict this method to non-null <T>. But it has users who pass
  //   iterables with null elements.)
  //
  // - @JointlyNullable means "@Nullable or no annotation"
  @CheckForNull
  public static <T extends @Nullable Object> T find(
      Iterable<? extends T> iterable,

     *
     * <p>This method is used when testing iterators without a known ordering. We poll the target
     * iterator's next element and pass it to the reference iterator through this method so it can
     * return the same element. This enables the assertion to pass and the reference iterator to
     * properly update its state.
     */
    void promoteToNext(E e) {
      if (nextElements.remove(e)) {