}
    return false;
  }

  @Override
  @ParametricNullness
  public final T next() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    state = State.NOT_READY;
    // Safe because hasNext() ensures that tryToComputeNext() has put a T into `next`.
    T result = uncheckedCastNullableTToT(next);
    next = null;
    return result;
  }

  @Override
  public final void remove() {

   * iterable. The key used to store that value in the multimap will be the result of calling the
   * function on that value. The resulting multimap is created as an immutable snapshot. In the
   * returned multimap, keys appear in the order they are first encountered, and the values
   * corresponding to each key appear in the same order as they are encountered.
   *

 *   }
 * }.visit(type);
 * }
 *
 * <p>One {@code Type} is visited at most once. The second time the same type is visited, it's
 * ignored by {@link #visit}. This avoids infinite recursion caused by recursive type bounds.
 *
 * <p>This class is not thread safe.
 *
 * @author Ben Yu
 */
abstract class TypeVisitor {

  private final Set<Type> visited = new HashSet<>();

  /**

@GwtCompatible
final class NullnessCasts {
  /**
   * Accepts a {@code @Nullable T} and returns a plain {@code T}, without performing any check that
   * that conversion is safe.
   *
   * <p>This method is intended to help with usages of type parameters that have {@linkplain
   * ParametricNullness parametric nullness}. If a type parameter instead ranges over only non-null

@GwtCompatible
final class NullnessCasts {
  /**
   * Accepts a {@code @Nullable T} and returns a plain {@code T}, without performing any check that
   * that conversion is safe.
   *
   * <p>This method is intended to help with usages of type parameters that have {@linkplain
   * ParametricNullness parametric nullness}. If a type parameter instead ranges over only non-null

   *         .addAll(WEBSAFE_COLORS)
   *         .add(new Color(0, 191, 255))
   *         .build();
   * }
   *
   * <p>Elements appear in the resulting list in the same order they were added to the builder.
   *
   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
   * multiple lists in series. Each new list contains all the elements of the ones created before
   * it.
   *
   * @since 2.0

        // there are bugs in various JVM that have problems doing this across
        // different filesystem. So we'll incur the small hit to actually copy
        // here and be safe. jvz.
        // ----------------------------------------------------------------------------

        try {
            Files.createDirectories(destination.toPath().getParent());

     * {@link #equals(Object)}, they have the same hashcode.
     *
     * @return a hash code value for this request
     */
    @Override
    int hashCode();

    /**
     * Returns {@code true} if the specified object is equal to this request.
     * Two requests are considered equal if they have the same type and all
     * significant fields are equal.
     *

  @Override
  public abstract int hashCode();

  /*
   * The implementation neither produces nor consumes any non-null instance of type C, so
   * casting the type parameter is safe.
   */
  @SuppressWarnings("unchecked")
  static <C extends Comparable> Cut<C> belowAll() {
    return (Cut<C>) BelowAll.INSTANCE;
  }

 * not consistent with {@code equals}.
 *
 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible