1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 #ifndef _LIBCPP___EXPECTED_UNEXPECTED_H
10 #define _LIBCPP___EXPECTED_UNEXPECTED_H
11 
12 #include <__config>
13 #include <__type_traits/conjunction.h>
14 #include <__type_traits/is_array.h>
15 #include <__type_traits/is_const.h>
16 #include <__type_traits/is_constructible.h>
17 #include <__type_traits/is_nothrow_constructible.h>
18 #include <__type_traits/is_object.h>
19 #include <__type_traits/is_same.h>
20 #include <__type_traits/is_swappable.h>
21 #include <__type_traits/is_volatile.h>
22 #include <__type_traits/negation.h>
23 #include <__type_traits/remove_cvref.h>
24 #include <__utility/forward.h>
25 #include <__utility/in_place.h>
26 #include <__utility/move.h>
27 #include <__utility/swap.h>
28 #include <initializer_list>
29 
30 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31 #  pragma GCC system_header
32 #endif
33 
34 #if _LIBCPP_STD_VER >= 23
35 
36 _LIBCPP_BEGIN_NAMESPACE_STD
37 
38 template <class _Err>
39 class unexpected;
40 
41 template <class _Tp>
42 struct __is_std_unexpected : false_type {};
43 
44 template <class _Err>
45 struct __is_std_unexpected<unexpected<_Err>> : true_type {};
46 
47 template <class _Tp>
48 using __valid_std_unexpected = _BoolConstant< //
49     is_object_v<_Tp> &&                       //
50     !is_array_v<_Tp> &&                       //
51     !__is_std_unexpected<_Tp>::value &&       //
52     !is_const_v<_Tp> &&                       //
53     !is_volatile_v<_Tp>                       //
54     >;
55 
56 template <class _Err>
57 class unexpected {
58   static_assert(__valid_std_unexpected<_Err>::value,
59                 "[expected.un.general] states a program that instantiates std::unexpected for a non-object type, an "
60                 "array type, a specialization of unexpected, or a cv-qualified type is ill-formed.");
61 
62 public:
63   _LIBCPP_HIDE_FROM_ABI constexpr unexpected(const unexpected&) = default;
64   _LIBCPP_HIDE_FROM_ABI constexpr unexpected(unexpected&&)      = default;
65 
66   template <class _Error = _Err>
67     requires(!is_same_v<remove_cvref_t<_Error>, unexpected> && //
68              !is_same_v<remove_cvref_t<_Error>, in_place_t> && //
69              is_constructible_v<_Err, _Error>)
70   _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(_Error&& __error) //
71       noexcept(is_nothrow_constructible_v<_Err, _Error>)                // strengthened
72       : __unex_(std::forward<_Error>(__error)) {}
73 
74   template <class... _Args>
75     requires is_constructible_v<_Err, _Args...>
76   _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(in_place_t, _Args&&... __args) //
77       noexcept(is_nothrow_constructible_v<_Err, _Args...>)                           // strengthened
78       : __unex_(std::forward<_Args>(__args)...) {}
79 
80   template <class _Up, class... _Args>
81     requires is_constructible_v<_Err, initializer_list<_Up>&, _Args...>
82   _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(in_place_t, initializer_list<_Up> __il, _Args&&... __args) //
83       noexcept(is_nothrow_constructible_v<_Err, initializer_list<_Up>&, _Args...>) // strengthened
84       : __unex_(__il, std::forward<_Args>(__args)...) {}
85 
86   _LIBCPP_HIDE_FROM_ABI constexpr unexpected& operator=(const unexpected&) = default;
87   _LIBCPP_HIDE_FROM_ABI constexpr unexpected& operator=(unexpected&&)      = default;
88 
89   _LIBCPP_HIDE_FROM_ABI constexpr const _Err& error() const& noexcept { return __unex_; }
90   _LIBCPP_HIDE_FROM_ABI constexpr _Err& error() & noexcept { return __unex_; }
91   _LIBCPP_HIDE_FROM_ABI constexpr const _Err&& error() const&& noexcept { return std::move(__unex_); }
92   _LIBCPP_HIDE_FROM_ABI constexpr _Err&& error() && noexcept { return std::move(__unex_); }
93 
94   _LIBCPP_HIDE_FROM_ABI constexpr void swap(unexpected& __other) noexcept(is_nothrow_swappable_v<_Err>) {
95     static_assert(is_swappable_v<_Err>, "unexpected::swap requires is_swappable_v<E> to be true");
96     using std::swap;
97     swap(__unex_, __other.__unex_);
98   }
99 
100   _LIBCPP_HIDE_FROM_ABI friend constexpr void swap(unexpected& __x, unexpected& __y) noexcept(noexcept(__x.swap(__y)))
101     requires is_swappable_v<_Err>
102   {
103     __x.swap(__y);
104   }
105 
106   template <class _Err2>
107   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const unexpected& __x, const unexpected<_Err2>& __y) {
108     return __x.__unex_ == __y.__unex_;
109   }
110 
111 private:
112   _Err __unex_;
113 };
114 
115 template <class _Err>
116 unexpected(_Err) -> unexpected<_Err>;
117 
118 _LIBCPP_END_NAMESPACE_STD
119 
120 #endif // _LIBCPP_STD_VER >= 23
121 
122 #endif // _LIBCPP___EXPECTED_UNEXPECTED_H
123