return true;
    }
    if (object instanceof ImmutableEnumSet) {
      object = ((ImmutableEnumSet<?>) object).delegate;
    }
    return delegate.equals(object);
  }

  @Override
  boolean isHashCodeFast() {
    return true;
  }

  @LazyInit private transient int hashCode;

  @Override
  public int hashCode() {
    int result = hashCode;

    if (object instanceof Set) {
      Set<?> that = (Set<?>) object;
      return that.isEmpty();
    }
    return false;
  }

  @GwtIncompatible // not used in GWT
  @Override
  boolean isHashCodeFast() {
    return true;
  }

  @Override
  public int hashCode() {
    return 0;
  }

  @GwtIncompatible
  @J2ktIncompatible