* already been re-added.
   */
  // Technically should accept RemovalNotification<? extends K, ? extends V>, but because
  // RemovalNotification is guaranteed covariant, let's make users' lives simpler.
  void onRemoval(RemovalNotification<K, V> notification);

  }

  @Override
  public T or(T defaultValue) {
    return checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
  }

  @SuppressWarnings("unchecked") // safe covariant cast
  @Override
  public Optional<T> or(Optional<? extends T> secondChoice) {
    return (Optional<T>) checkNotNull(secondChoice);
  }

  @Override
  public T or(Supplier<? extends T> supplier) {

  @Override
  ImmutableCollection<E> delegateCollection() {
    return delegate;
  }

  ImmutableList<? extends E> delegateList() {
    return delegateList;
  }

  @SuppressWarnings("unchecked") // safe covariant cast!
  @Override
  public UnmodifiableListIterator<E> listIterator(int index) {
    return (UnmodifiableListIterator<E>) delegateList.listIterator(index);
  }

  @GwtIncompatible // not present in emulated superclass

   * already been re-added.
   */
  // Technically should accept RemovalNotification<? extends K, ? extends V>, but because
  // RemovalNotification is guaranteed covariant, let's make users' lives simpler.
  void onRemoval(RemovalNotification<K, V> notification);

  @Override
  ImmutableCollection<E> delegateCollection() {
    return delegate;
  }

  ImmutableList<? extends E> delegateList() {
    return delegateList;
  }

  @SuppressWarnings("unchecked") // safe covariant cast!
  @Override
  public UnmodifiableListIterator<E> listIterator(int index) {
    return (UnmodifiableListIterator<E>) delegateList.listIterator(index);
  }

  @GwtIncompatible // not present in emulated superclass

       * TODO: When given an ImmutableList that's a sublist, copy the referenced
       * portion of the array into a new array to save space?
       */
      @SuppressWarnings("unchecked") // all supported methods are covariant
      ImmutableCollection<E> list = (ImmutableCollection<E>) elements;
      return list.asList();
    }
    return copyFromCollection(elements);
  }

  @JsMethod

    if (map instanceof ImmutableClassToInstanceMap) {
      @SuppressWarnings("rawtypes") // JDT-based J2KT Java frontend does not permit the direct cast
      Map rawMap = map;
      @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
      ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap<B>) rawMap;
      return cast;
    }
    return new Builder<B>().putAll(map).build();
  }

    if (map instanceof ImmutableClassToInstanceMap) {
      @SuppressWarnings("rawtypes") // JDT-based J2KT Java frontend does not permit the direct cast
      Map rawMap = map;
      @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
      ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap<B>) rawMap;
      return cast;
    }
    return new Builder<B>().putAll(map).build();
  }

    FluentIterable<? extends Number> numbers = getSomeNumbers();

    // Sadly, the following is what users will have to do in some circumstances.

    @SuppressWarnings("unchecked") // safe covariant cast
    Optional<Number> first = (Optional<Number>) numbers.first();
    Number value = first.or(0.5); // fine
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester

    UnmodifiableTable(Table<? extends R, ? extends C, ? extends V> delegate) {
      this.delegate = checkNotNull(delegate);
    }

    @SuppressWarnings("unchecked") // safe, covariant cast
    @Override
    protected Table<R, C, V> delegate() {
      return (Table<R, C, V>) delegate;
    }

    @Override
    public Set<Cell<R, C, V>> cellSet() {