checkArgument(!map.isEmpty());
    return getDeclaringClassOrObjectForJ2cl(map.keySet().iterator().next());
  }

  private static <V extends Enum<V>> Class<V> inferValueTypeOrObjectUnderJ2cl(Map<?, V> map) {
    if (map instanceof EnumBiMap) {
      return ((EnumBiMap<?, V>) map).valueTypeOrObjectUnderJ2cl;
    }
    checkArgument(!map.isEmpty());
    return getDeclaringClassOrObjectForJ2cl(map.values().iterator().next());
  }

    checkArgument(!map.isEmpty());
    return getDeclaringClassOrObjectForJ2cl(map.keySet().iterator().next());
  }

  private static <V extends Enum<V>> Class<V> inferValueTypeOrObjectUnderJ2cl(Map<?, V> map) {
    if (map instanceof EnumBiMap) {
      return ((EnumBiMap<?, V>) map).valueTypeOrObjectUnderJ2cl;
    }
    checkArgument(!map.isEmpty());
    return getDeclaringClassOrObjectForJ2cl(map.values().iterator().next());
  }

   * that reclamation becomes important.
   */
  @J2ktIncompatible
  static MapMaker tryWeakKeys(MapMaker mapMaker) {
    return mapMaker.weakKeys();
  }

  static <E extends Enum<E>> Class<E> getDeclaringClassOrObjectForJ2cl(E e) {
    return e.getDeclaringClass();
  }

  static int reduceIterationsIfGwt(int iterations) {
    return iterations;
  }

  static int reduceExponentIfGwt(int exponent) {

    @JsProperty
    void setLength(int length);
  }

  static MapMaker tryWeakKeys(MapMaker mapMaker) {
    return mapMaker;
  }

  static <E extends Enum<E>> Class<E> getDeclaringClassOrObjectForJ2cl(E e) {
    Class<E> classOrNull = getDeclaringClassOrNullForJ2cl(e);
    @SuppressWarnings("unchecked")
    Class<E> result = classOrNull == null ? (Class<E>) (Class<?>) Object.class : classOrNull;