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
38template <class _Err>
39class unexpected;
40
41template <class _Tp>
42struct __is_std_unexpected : false_type {};
43
44template <class _Err>
45struct __is_std_unexpected<unexpected<_Err>> : true_type {};
46
47template <class _Tp>
48using __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
56template <class _Err>
57class 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
62public:
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
111private:
112  _Err __unex_;
113};
114
115template <class _Err>
116unexpected(_Err) -> unexpected<_Err>;
117
118_LIBCPP_END_NAMESPACE_STD
119
120#endif // _LIBCPP_STD_VER >= 23
121
122#endif // _LIBCPP___EXPECTED_UNEXPECTED_H
123