v1/__expected/unexpected.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009 #ifndef _LIBCPP___EXPECTED_UNEXPECTED_H
0010 #define _LIBCPP___EXPECTED_UNEXPECTED_H
0011
0012 #include <__config>
0013 #include <__type_traits/conjunction.h>
0014 #include <__type_traits/is_array.h>
0015 #include <__type_traits/is_const.h>
0016 #include <__type_traits/is_constructible.h>
0017 #include <__type_traits/is_nothrow_constructible.h>
0018 #include <__type_traits/is_object.h>
0019 #include <__type_traits/is_same.h>
0020 #include <__type_traits/is_swappable.h>
0021 #include <__type_traits/is_volatile.h>
0022 #include <__type_traits/negation.h>
0023 #include <__type_traits/remove_cvref.h>
0024 #include <__utility/forward.h>
0025 #include <__utility/in_place.h>
0026 #include <__utility/move.h>
0027 #include <__utility/swap.h>
0028 #include <initializer_list>
0029
0030 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0031 #  pragma GCC system_header
0032 #endif
0033
0034 _LIBCPP_PUSH_MACROS
0035 #include <__undef_macros>
0036
0037 #if _LIBCPP_STD_VER >= 23
0038
0039 _LIBCPP_BEGIN_NAMESPACE_STD
0040
0041 template <class _Err>
0042 class unexpected;
0043
0044 template <class _Tp>
0045 struct __is_std_unexpected : false_type {};
0046
0047 template <class _Err>
0048 struct __is_std_unexpected<unexpected<_Err>> : true_type {};
0049
0050 template <class _Tp>
0051 using __valid_std_unexpected _LIBCPP_NODEBUG = _BoolConstant< //
0052     is_object_v<_Tp> &&                                       //
0053     !is_array_v<_Tp> &&                                       //
0054     !__is_std_unexpected<_Tp>::value &&                       //
0055     !is_const_v<_Tp> &&                                       //
0056     !is_volatile_v<_Tp>                                       //
0057     >;
0058
0059 template <class _Err>
0060 class unexpected {
0061   static_assert(__valid_std_unexpected<_Err>::value,
0062                 "[expected.un.general] states a program that instantiates std::unexpected for a non-object type, an "
0063                 "array type, a specialization of unexpected, or a cv-qualified type is ill-formed.");
0064
0065 public:
0066   _LIBCPP_HIDE_FROM_ABI constexpr unexpected(const unexpected&) = default;
0067   _LIBCPP_HIDE_FROM_ABI constexpr unexpected(unexpected&&)      = default;
0068
0069   template <class _Error = _Err>
0070     requires(!is_same_v<remove_cvref_t<_Error>, unexpected> && //
0071              !is_same_v<remove_cvref_t<_Error>, in_place_t> && //
0072              is_constructible_v<_Err, _Error>)
0073   _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(_Error&& __error) //
0074       noexcept(is_nothrow_constructible_v<_Err, _Error>)                // strengthened
0075       : __unex_(std::forward<_Error>(__error)) {}
0076
0077   template <class... _Args>
0078     requires is_constructible_v<_Err, _Args...>
0079   _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(in_place_t, _Args&&... __args) //
0080       noexcept(is_nothrow_constructible_v<_Err, _Args...>)                           // strengthened
0081       : __unex_(std::forward<_Args>(__args)...) {}
0082
0083   template <class _Up, class... _Args>
0084     requires is_constructible_v<_Err, initializer_list<_Up>&, _Args...>
0085   _LIBCPP_HIDE_FROM_ABI constexpr explicit unexpected(in_place_t, initializer_list<_Up> __il, _Args&&... __args) //
0086       noexcept(is_nothrow_constructible_v<_Err, initializer_list<_Up>&, _Args...>) // strengthened
0087       : __unex_(__il, std::forward<_Args>(__args)...) {}
0088
0089   _LIBCPP_HIDE_FROM_ABI constexpr unexpected& operator=(const unexpected&) = default;
0090   _LIBCPP_HIDE_FROM_ABI constexpr unexpected& operator=(unexpected&&)      = default;
0091
0092   _LIBCPP_HIDE_FROM_ABI constexpr const _Err& error() const& noexcept { return __unex_; }
0093   _LIBCPP_HIDE_FROM_ABI constexpr _Err& error() & noexcept { return __unex_; }
0094   _LIBCPP_HIDE_FROM_ABI constexpr const _Err&& error() const&& noexcept { return std::move(__unex_); }
0095   _LIBCPP_HIDE_FROM_ABI constexpr _Err&& error() && noexcept { return std::move(__unex_); }
0096
0097   _LIBCPP_HIDE_FROM_ABI constexpr void swap(unexpected& __other) noexcept(is_nothrow_swappable_v<_Err>) {
0098     static_assert(is_swappable_v<_Err>, "unexpected::swap requires is_swappable_v<E> to be true");
0099     using std::swap;
0100     swap(__unex_, __other.__unex_);
0101   }
0102
0103   _LIBCPP_HIDE_FROM_ABI friend constexpr void swap(unexpected& __x, unexpected& __y) noexcept(noexcept(__x.swap(__y)))
0104     requires is_swappable_v<_Err>
0105   {
0106     __x.swap(__y);
0107   }
0108
0109   template <class _Err2>
0110   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const unexpected& __x, const unexpected<_Err2>& __y) {
0111     return __x.__unex_ == __y.error();
0112   }
0113
0114 private:
0115   _Err __unex_;
0116 };
0117
0118 template <class _Err>
0119 unexpected(_Err) -> unexpected<_Err>;
0120
0121 _LIBCPP_END_NAMESPACE_STD
0122
0123 #endif // _LIBCPP_STD_VER >= 23
0124
0125 _LIBCPP_POP_MACROS
0126
0127 #endif // _LIBCPP___EXPECTED_UNEXPECTED_H