}

  /**
   * Wraps the {@code setValue} implementation of an {@code Entry} to enforce the class constraint.
   */
  private static <B extends @Nullable Object> Entry<Class<? extends @NonNull B>, B> checkedEntry(
      final Entry<Class<? extends @NonNull B>, B> entry) {
    return new ForwardingMapEntry<Class<? extends @NonNull B>, B>() {
      @Override
      protected Entry<Class<? extends @NonNull B>, B> delegate() {