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_LIBCPP_PUSH_MACROS
35#include <__undef_macros>
36
37#if _LIBCPP_STD_VER >= 23
38
39_LIBCPP_BEGIN_NAMESPACE_STD
40
41template <class _Err>
42class unexpected;
43
44template <class _Tp>
45struct __is_std_unexpected : false_type {};
46
47template <class _Err>
48struct __is_std_unexpected<unexpected<_Err>> : true_type {};
49
50template <class _Tp>
51using __valid_std_unexpected _LIBCPP_NODEBUG = _BoolConstant< //
52 is_object_v<_Tp> && //
53 !is_array_v<_Tp> && //
54 !__is_std_unexpected<_Tp>::value && //
55 !is_const_v<_Tp> && //
56 !is_volatile_v<_Tp> //
57 >;
58
59template <class _Err>
60class unexpected {
61 static_assert(__valid_std_unexpected<_Err>::value,
62 "[expected.un.general] states a program that instantiates std::unexpected for a non-object type, an "
63 "array type, a specialization of unexpected, or a cv-qualified type is ill-formed.");
64
65public:
66 _LIBCPP_HIDE_FROM_ABI constexpr unexpected(const unexpected&) = default;
67 _LIBCPP_HIDE_FROM_ABI constexpr unexpected(unexpected&&) = default;
68
69 template <class _Error = _Err>
70 requires(!is_same_v<remove_cvref_t<_Error>, unexpected> && //
71 !is_same_v<remove_cvref_t<_Error>, in_place_t> && //
72 is_constructible_v<_Err, _Error>)
73 _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(_Error&& __error) //
74 noexcept(is_nothrow_constructible_v<_Err, _Error>) // strengthened
75 : __unex_(std::forward<_Error>(__error)) {}
76
77 template <class... _Args>
78 requires is_constructible_v<_Err, _Args...>
79 _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(in_place_t, _Args&&... __args) //
80 noexcept(is_nothrow_constructible_v<_Err, _Args...>) // strengthened
81 : __unex_(std::forward<_Args>(__args)...) {}
82
83 template <class _Up, class... _Args>
84 requires is_constructible_v<_Err, initializer_list<_Up>&, _Args...>
85 _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(in_place_t, initializer_list<_Up> __il, _Args&&... __args) //
86 noexcept(is_nothrow_constructible_v<_Err, initializer_list<_Up>&, _Args...>) // strengthened
87 : __unex_(__il, std::forward<_Args>(__args)...) {}
88
89 _LIBCPP_HIDE_FROM_ABI constexpr unexpected& operator=(const unexpected&) = default;
90 _LIBCPP_HIDE_FROM_ABI constexpr unexpected& operator=(unexpected&&) = default;
91
92 _LIBCPP_HIDE_FROM_ABI constexpr const _Err& error() const& noexcept { return __unex_; }
93 _LIBCPP_HIDE_FROM_ABI constexpr _Err& error() & noexcept { return __unex_; }
94 _LIBCPP_HIDE_FROM_ABI constexpr const _Err&& error() const&& noexcept { return std::move(__unex_); }
95 _LIBCPP_HIDE_FROM_ABI constexpr _Err&& error() && noexcept { return std::move(__unex_); }
96
97 _LIBCPP_HIDE_FROM_ABI constexpr void swap(unexpected& __other) noexcept(is_nothrow_swappable_v<_Err>) {
98 static_assert(is_swappable_v<_Err>, "unexpected::swap requires is_swappable_v<E> to be true");
99 using std::swap;
100 swap(__unex_, __other.__unex_);
101 }
102
103 _LIBCPP_HIDE_FROM_ABI friend constexpr void swap(unexpected& __x, unexpected& __y) noexcept(noexcept(__x.swap(__y)))
104 requires is_swappable_v<_Err>
105 {
106 __x.swap(__y);
107 }
108
109 template <class _Err2>
110 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const unexpected& __x, const unexpected<_Err2>& __y) {
111 return __x.__unex_ == __y.error();
112 }
113
114private:
115 _Err __unex_;
116};
117
118template <class _Err>
119unexpected(_Err) -> unexpected<_Err>;
120
121_LIBCPP_END_NAMESPACE_STD
122
123#endif // _LIBCPP_STD_VER >= 23
124
125_LIBCPP_POP_MACROS
126
127#endif // _LIBCPP___EXPECTED_UNEXPECTED_H
128