libcxx/include/__cxx03/__expected/unexpected.h

   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 <__cxx03/__config>
  13 #include <__cxx03/__type_traits/conjunction.h>
  14 #include <__cxx03/__type_traits/is_array.h>
  15 #include <__cxx03/__type_traits/is_const.h>
  16 #include <__cxx03/__type_traits/is_constructible.h>
  17 #include <__cxx03/__type_traits/is_nothrow_constructible.h>
  18 #include <__cxx03/__type_traits/is_object.h>
  19 #include <__cxx03/__type_traits/is_same.h>
  20 #include <__cxx03/__type_traits/is_swappable.h>
  21 #include <__cxx03/__type_traits/is_volatile.h>
  22 #include <__cxx03/__type_traits/negation.h>
  23 #include <__cxx03/__type_traits/remove_cvref.h>
  24 #include <__cxx03/__utility/forward.h>
  25 #include <__cxx03/__utility/in_place.h>
  26 #include <__cxx03/__utility/move.h>
  27 #include <__cxx03/__utility/swap.h>
  28 #include <__cxx03/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 <__cxx03/__undef_macros>
  36
  37 #if _LIBCPP_STD_VER >= 23
  38
  39 _LIBCPP_BEGIN_NAMESPACE_STD
  40
  41 template <class _Err>
  42 class unexpected;
  43
  44 template <class _Tp>
  45 struct __is_std_unexpected : false_type {};
  46
  47 template <class _Err>
  48 struct __is_std_unexpected<unexpected<_Err>> : true_type {};
  49
  50 template <class _Tp>
  51 using __valid_std_unexpected = _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
  59 template <class _Err>
  60 class 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
  65 public:
  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.__unex_;
 112   }
 113
 114 private:
 115   _Err __unex_;
 116 };
 117
 118 template <class _Err>
 119 unexpected(_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