*
 * @author Jared Levy
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
class EmptyImmutableListMultimap extends ImmutableListMultimap<Object, Object> {
  static final EmptyImmutableListMultimap INSTANCE = new EmptyImmutableListMultimap();

  private EmptyImmutableListMultimap() {
    super(ImmutableMap.<Object, ImmutableList<Object>>of(), 0);
  }

  /*

 *
 * @author Emily Soldal
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
final class AllEqualOrdering extends Ordering<@Nullable Object> implements Serializable {
  static final AllEqualOrdering INSTANCE = new AllEqualOrdering();

  @Override
  @SuppressWarnings("UnusedVariable") // intentionally weird Comparator
  public int compare(@CheckForNull Object left, @CheckForNull Object right) {
    return 0;
  }

 *
 * @author Jared Levy
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
class EmptyImmutableListMultimap extends ImmutableListMultimap<Object, Object> {
  static final EmptyImmutableListMultimap INSTANCE = new EmptyImmutableListMultimap();

  private EmptyImmutableListMultimap() {
    super(ImmutableMap.<Object, ImmutableList<Object>>of(), 0);
  }

  /*

  /**
   * Compares the specified object with this instance for equality. Returns {@code true} if the
   * given object is also a {@code MapDifference} and the values returned by the {@link
   * #entriesOnlyOnLeft()}, {@link #entriesOnlyOnRight()}, {@link #entriesInCommon()} and {@link
   * #entriesDiffering()} of the two instances are equal.
   */
  @Override
  boolean equals(@CheckForNull Object object);

  /** Creates an empty {@code CompactLinkedHashSet} instance. */
  public static <E extends @Nullable Object> CompactLinkedHashSet<E> create() {
    return new CompactLinkedHashSet<>();
  }

  /**
   * Creates a <i>mutable</i> {@code CompactLinkedHashSet} instance containing the elements of the
   * given collection in the order returned by the collection's iterator.
   *

    this.host = host;
    this.port = port;
    this.hasBracketlessColons = hasBracketlessColons;
  }

  /**
   * Returns the portion of this {@code HostAndPort} instance that should represent the hostname or
   * IPv4/IPv6 literal.
   *
   * <p>A successful parse does not imply any degree of sanity in this field. For additional
   * validation, see the {@link HostSpecifier} class.
   *

  // TODO(user): cache all field accesses in local vars

  /** Creates an empty {@code CompactHashSet} instance. */
  public static <E extends @Nullable Object> CompactHashSet<E> create() {
    return new CompactHashSet<>();
  }

  /**
   * Creates a <i>mutable</i> {@code CompactHashSet} instance containing the elements of the given
   * collection in unspecified order.
   *

  public static <V extends @Nullable Object> ListenableFuture<V> immediateCancelledFuture() {
    ListenableFuture<Object> instance = ImmediateCancelledFuture.INSTANCE;
    if (instance != null) {
      return (ListenableFuture<V>) instance;
    }
    return new ImmediateCancelledFuture<>();
  }

  /**

   * Returns a {@link Writer} that simply discards written chars.
   *
   * @since 15.0
   */
  public static Writer nullWriter() {
    return NullWriter.INSTANCE;
  }

  private static final class NullWriter extends Writer {

    private static final NullWriter INSTANCE = new NullWriter();

    @Override
    public void write(int c) {}

    @Override
    public void write(char[] cbuf) {

	val          atomic.Pointer[T]
	lastUpdateMs atomic.Int64
	updating     sync.Mutex
}

// New allocates a new cached value instance. Tt must be initialized with
// `.TnitOnce`.
func New[T any]() *Cache[T] {
	return &Cache[T]{}
}

// NewFromFunc allocates a new cached value instance and initializes it with an
// update function, making it ready for use.