cxx-benchmarks/test-smart-factory.cpp

#include <memory>
#include <type_traits>

class C {
protected:
  struct Protected {
  private:
    Protected() {};
  public:
    static Protected make() { return { }; }
  };
  int m_x;

private:
  struct Private {
  private:
    Private() {};
  public:
    static Private make() { return { }; }
  };
  int m_y;

public:
  /* private constructor: */
  C(Private, int x, int y) : m_x(x), m_y(y) { }
  /* protected constructor: */
  C(Protected, int x) : C(Private::make(), x, 2*x) { }

  void leak_private_type(Private) { }

  static std::unique_ptr<C> Create(int x) {
    return std::unique_ptr<C>(new C(Private::make(), x, 2*x));
  }
};

class D : public C {
private:
  struct Private { };
public:
  D(Private&, int x) : C(Protected::make(), x) { }

  static std::shared_ptr<D> Create(int x) {
    Private p;
    return std::make_shared<D>(p, 4*x);
  }
};


class A {
   struct this_is_private {
   };

 public:
   explicit A(const this_is_private &, int) {}

   static ::std::shared_ptr<A> create(int x) {
      return ::std::make_shared<A>(this_is_private{}, x);
   }

 protected:
   A(const A &) = delete;
   const A &operator =(const A &) = delete;
};

::std::shared_ptr<A> foo(int x)
{
   return A::create(x);
}


  /* usage: decltype(return_args(&Class::memberfunction)) */
  template<typename Base, typename Result, typename... Args>
  std::tuple<Args...> return_args(Result (Base::*func)(Args...));

  /* usage: decltype(result_of(&Class::memberfunction)) */
  template<typename Base, typename Result, typename... Args>
  Result result_of(Result (Base::*func)(Args...));

  /* usage: decay_tuple_element<0, decltype(return_args(&Class::memberfunction))> */
  template <size_t i, typename Tuple>
  using decay_tuple_element = typename std::decay<typename std::tuple_element<i, Tuple>::type>::type;


  struct _is_static_castable_impl
  {
    template<typename _From, typename _To, typename = decltype(static_cast<_To>(std::declval<_From>()))>
    static std::true_type __test(int);

    template<typename, typename>
    static std::false_type __test(...);
  };

  template<typename _From, typename _To>
  struct is_static_castable
  : public _is_static_castable_impl
  {
    typedef decltype(__test<_From, _To>(0)) type;
  };

  template<typename _From, typename _To>
  using is_static_castable_t = typename is_static_castable<_From, _To>::type;



int main() {
  auto c = C::Create(0);
  auto d = D::Create(0);

  typedef decay_tuple_element<0, decltype(return_args(&C::leak_private_type))> Private;
  Private::make();


  auto a1 = foo(0);
  auto a2 = std::shared_ptr<A>(new A({}, 0));

//  C c1({}, 0, 0);
}