//===----------------------------------------------------------------------===//
//
// 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_IS_DESTRUCTIBLE_H
#define _LIBCPP___TYPE_TRAITS_IS_DESTRUCTIBLE_H

#include <__config>
#include <__type_traits/integral_constant.h>
#include <__type_traits/is_function.h>
#include <__type_traits/is_reference.h>
#include <__type_traits/remove_all_extents.h>
#include <__utility/declval.h>

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

_LIBCPP_BEGIN_NAMESPACE_STD

#if __has_keyword(__is_destructible)

template<class _Tp>
struct _LIBCPP_TEMPLATE_VIS is_destructible : _BoolConstant<__is_destructible(_Tp)> { };

#if _LIBCPP_STD_VER > 14
template <class _Tp>
inline constexpr bool is_destructible_v = __is_destructible(_Tp);
#endif

#else // __has_keyword(__is_destructible)

//  if it's a reference, return true
//  if it's a function, return false
//  if it's   void,     return false
//  if it's an array of unknown bound, return false
//  Otherwise, return "declval<_Up&>().~_Up()" is well-formed
//    where _Up is remove_all_extents<_Tp>::type

template <class>
struct __is_destructible_apply { typedef int type; };

template <typename _Tp>
struct __is_destructor_wellformed {
    template <typename _Tp1>
    static true_type  __test (
        typename __is_destructible_apply<decltype(declval<_Tp1&>().~_Tp1())>::type
    );

    template <typename _Tp1>
    static false_type __test (...);

    static const bool value = decltype(__test<_Tp>(12))::value;
};

template <class _Tp, bool>
struct __destructible_imp;

template <class _Tp>
struct __destructible_imp<_Tp, false>
   : public integral_constant<bool,
        __is_destructor_wellformed<typename remove_all_extents<_Tp>::type>::value> {};

template <class _Tp>
struct __destructible_imp<_Tp, true>
    : public true_type {};

template <class _Tp, bool>
struct __destructible_false;

template <class _Tp>
struct __destructible_false<_Tp, false> : public __destructible_imp<_Tp, is_reference<_Tp>::value> {};

template <class _Tp>
struct __destructible_false<_Tp, true> : public false_type {};

template <class _Tp>
struct is_destructible
    : public __destructible_false<_Tp, is_function<_Tp>::value> {};

template <class _Tp>
struct is_destructible<_Tp[]>
    : public false_type {};

template <>
struct is_destructible<void>
    : public false_type {};

#if _LIBCPP_STD_VER > 14
template <class _Tp>
inline constexpr bool is_destructible_v = is_destructible<_Tp>::value;
#endif

#endif // __has_keyword(__is_destructible)

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___TYPE_TRAITS_IS_DESTRUCTIBLE_H