}
      return newCapacity;
    }

    Builder() {}

    /**
     * Adds {@code element} to the {@code ImmutableCollection} being built.
     *
     * <p>Note that each builder class covariantly returns its own type from this method.
     *
     * @param element the element to add
     * @return this {@code Builder} instance
     * @throws NullPointerException if {@code element} is null
     */

  }

  /**
   * Returns a resolver that resolves types "covariantly".
   *
   * <p>For example, when resolving {@code List<T>} in the context of {@code ArrayList<?>}, {@code
   * <T>} is covariantly resolved to {@code <?>} such that return type of {@code List::get} is
   * {@code <?>}.
   */
  static TypeResolver covariantly(Type contextType) {

  }

  /**
   * Returns a resolver that resolves types "covariantly".
   *
   * <p>For example, when resolving {@code List<T>} in the context of {@code ArrayList<?>}, {@code
   * <T>} is covariantly resolved to {@code <?>} such that return type of {@code List::get} is
   * {@code <?>}.
   */
  static TypeResolver covariantly(Type contextType) {

      Iterator<? extends T> iterator) {
    if (iterator instanceof PeekingImpl) {
      // Safe to cast <? extends T> to <T> because PeekingImpl only uses T
      // covariantly (and cannot be subclassed to add non-covariant uses).
      @SuppressWarnings("unchecked")
      PeekingImpl<T> peeking = (PeekingImpl<T>) iterator;
      return peeking;
    }
    return new PeekingImpl<>(iterator);
  }

  @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

  }

  @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

       * 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

    /**
     * Represent an invariant type argument.
     * e.g. `<T>`
     */
    INVARIANT,

    /**
     * Represent a covariant type argument.
     * Also known as "extends-bound" or "upper bound".
     * e.g. `<? extends T>`
     */
    COVARIANT,

    /**
     * Represent a contravariant type argument.
     * Also known as "super-bound" or "lower bound".
     * e.g. `<? super T>`
     */

    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