//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___TYPE_TRAITS_PROMOTE_H
#define _LIBCPP___TYPE_TRAITS_PROMOTE_H

#include <__config>
#include <__type_traits/integral_constant.h>
#include <__type_traits/is_same.h>
#include <__utility/declval.h>
#include <cstddef>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _Tp>
struct __numeric_type
{
   static void __test(...);
   static float __test(float);
   static double __test(char);
   static double __test(int);
   static double __test(unsigned);
   static double __test(long);
   static double __test(unsigned long);
   static double __test(long long);
   static double __test(unsigned long long);
   static double __test(double);
   static long double __test(long double);

   typedef decltype(__test(declval<_Tp>())) type;
   static const bool value = _IsNotSame<type, void>::value;
};

template <>
struct __numeric_type<void>
{
   static const bool value = true;
};

template <class _A1, class _A2 = void, class _A3 = void,
          bool = __numeric_type<_A1>::value &&
                 __numeric_type<_A2>::value &&
                 __numeric_type<_A3>::value>
class __promote_imp
{
public:
    static const bool value = false;
};

template <class _A1, class _A2, class _A3>
class __promote_imp<_A1, _A2, _A3, true>
{
private:
    typedef typename __promote_imp<_A1>::type __type1;
    typedef typename __promote_imp<_A2>::type __type2;
    typedef typename __promote_imp<_A3>::type __type3;
public:
    typedef decltype(__type1() + __type2() + __type3()) type;
    static const bool value = true;
};

template <class _A1, class _A2>
class __promote_imp<_A1, _A2, void, true>
{
private:
    typedef typename __promote_imp<_A1>::type __type1;
    typedef typename __promote_imp<_A2>::type __type2;
public:
    typedef decltype(__type1() + __type2()) type;
    static const bool value = true;
};

template <class _A1>
class __promote_imp<_A1, void, void, true>
{
public:
    typedef typename __numeric_type<_A1>::type type;
    static const bool value = true;
};

template <class _A1, class _A2 = void, class _A3 = void>
class __promote : public __promote_imp<_A1, _A2, _A3> {};

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___TYPE_TRAITS_PROMOTE_H