import org.jspecify.annotations.Nullable;

/**
 * GWT emulated version of {@link ImmutableList}. TODO(cpovirk): more doc
 *
 * @author Hayward Chan
 */
abstract class ForwardingImmutableList<E> extends ImmutableList<E> {

  ForwardingImmutableList() {}

  abstract List<E> delegateList();

  @Override
  public int indexOf(@Nullable Object object) {
    return delegateList().indexOf(object);
  }

  @Override

import java.util.List;

/**
 * GWT emulated version of {@link RegularImmutableList}.
 *
 * @author Hayward Chan
 */
final class RegularImmutableList<E> extends ForwardingImmutableList<E> {
  static final ImmutableList<Object> EMPTY = new RegularImmutableList<Object>(emptyList());

  private final List<E> delegate;

  RegularImmutableList(List<E> delegate) {

import java.util.List;

/**
 * GWT emulated version of {@link SingletonImmutableList}.
 *
 * @author Hayward Chan
 */
final class SingletonImmutableList<E> extends ForwardingImmutableList<E> {
  private final transient List<E> delegate;
  private final E element;

  SingletonImmutableList(E element) {
    this.delegate = singletonList(checkNotNull(element));
    this.element = element;
  }