public ConstructorParameterNotInstantiable(@SuppressWarnings("unused") NotInstantiable x) {}
  }

  static class ConstructorParameterMapOfNotInstantiable {
    private final Map<NotInstantiable, NotInstantiable> m;

    public ConstructorParameterMapOfNotInstantiable(Map<NotInstantiable, NotInstantiable> m) {
      this.m = checkNotNull(m);
    }

    @Override