1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___TYPE_TRAITS_IS_DESTRUCTIBLE_H
10 #define _LIBCPP___TYPE_TRAITS_IS_DESTRUCTIBLE_H
11 
12 #include <__config>
13 #include <__type_traits/integral_constant.h>
14 #include <__type_traits/is_function.h>
15 #include <__type_traits/is_reference.h>
16 #include <__type_traits/remove_all_extents.h>
17 #include <__utility/declval.h>
18 
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #  pragma GCC system_header
21 #endif
22 
23 _LIBCPP_BEGIN_NAMESPACE_STD
24 
25 #if __has_builtin(__is_destructible)
26 
27 template <class _Tp>
28 struct _LIBCPP_TEMPLATE_VIS is_destructible : _BoolConstant<__is_destructible(_Tp)> {};
29 
30 #  if _LIBCPP_STD_VER >= 17
31 template <class _Tp>
32 inline constexpr bool is_destructible_v = __is_destructible(_Tp);
33 #  endif
34 
35 #else // __has_builtin(__is_destructible)
36 
37 //  if it's a reference, return true
38 //  if it's a function, return false
39 //  if it's   void,     return false
40 //  if it's an array of unknown bound, return false
41 //  Otherwise, return "declval<_Up&>().~_Up()" is well-formed
42 //    where _Up is remove_all_extents<_Tp>::type
43 
44 template <class>
45 struct __is_destructible_apply {
46   typedef int type;
47 };
48 
49 template <typename _Tp>
50 struct __is_destructor_wellformed {
51   template <typename _Tp1>
52   static true_type __test(typename __is_destructible_apply<decltype(std::declval<_Tp1&>().~_Tp1())>::type);
53 
54   template <typename _Tp1>
55   static false_type __test(...);
56 
57   static const bool value = decltype(__test<_Tp>(12))::value;
58 };
59 
60 template <class _Tp, bool>
61 struct __destructible_imp;
62 
63 template <class _Tp>
64 struct __destructible_imp<_Tp, false>
65     : public integral_constant<bool, __is_destructor_wellformed<__remove_all_extents_t<_Tp> >::value> {};
66 
67 template <class _Tp>
68 struct __destructible_imp<_Tp, true> : public true_type {};
69 
70 template <class _Tp, bool>
71 struct __destructible_false;
72 
73 template <class _Tp>
74 struct __destructible_false<_Tp, false> : public __destructible_imp<_Tp, is_reference<_Tp>::value> {};
75 
76 template <class _Tp>
77 struct __destructible_false<_Tp, true> : public false_type {};
78 
79 template <class _Tp>
80 struct is_destructible : public __destructible_false<_Tp, is_function<_Tp>::value> {};
81 
82 template <class _Tp>
83 struct is_destructible<_Tp[]> : public false_type {};
84 
85 template <>
86 struct is_destructible<void> : public false_type {};
87 
88 #  if _LIBCPP_STD_VER >= 17
89 template <class _Tp>
90 inline constexpr bool is_destructible_v = is_destructible<_Tp>::value;
91 #  endif
92 
93 #endif // __has_builtin(__is_destructible)
94 
95 _LIBCPP_END_NAMESPACE_STD
96 
97 #endif // _LIBCPP___TYPE_TRAITS_IS_DESTRUCTIBLE_H
98