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
10#ifndef _LIBCPP_VARIANT
11#define _LIBCPP_VARIANT
12
13/*
14 variant synopsis
15
16namespace std {
17
18 // 20.7.2, class template variant
19 template <class... Types>
20 class variant {
21 public:
22
23 // 20.7.2.1, constructors
24 constexpr variant() noexcept(see below);
25 constexpr variant(const variant&);
26 constexpr variant(variant&&) noexcept(see below);
27
28 template <class T> constexpr variant(T&&) noexcept(see below);
29
30 template <class T, class... Args>
31 constexpr explicit variant(in_place_type_t<T>, Args&&...);
32
33 template <class T, class U, class... Args>
34 constexpr explicit variant(
35 in_place_type_t<T>, initializer_list<U>, Args&&...);
36
37 template <size_t I, class... Args>
38 constexpr explicit variant(in_place_index_t<I>, Args&&...);
39
40 template <size_t I, class U, class... Args>
41 constexpr explicit variant(
42 in_place_index_t<I>, initializer_list<U>, Args&&...);
43
44 // 20.7.2.2, destructor
45 constexpr ~variant(); // constexpr since c++20
46
47 // 20.7.2.3, assignment
48 constexpr variant& operator=(const variant&);
49 constexpr variant& operator=(variant&&) noexcept(see below);
50
51 template <class T>
52 constexpr variant& operator=(T&&) noexcept(see below); // constexpr since c++20
53
54 // 20.7.2.4, modifiers
55 template <class T, class... Args>
56 constexpr T& emplace(Args&&...); // constexpr since c++20
57
58 template <class T, class U, class... Args>
59 constexpr T& emplace(initializer_list<U>, Args&&...); // constexpr since c++20
60
61 template <size_t I, class... Args>
62 constexpr variant_alternative_t<I, variant>& emplace(Args&&...); // constexpr since c++20
63
64 template <size_t I, class U, class... Args>
65 constexpr variant_alternative_t<I, variant>&
66 emplace(initializer_list<U>, Args&&...); // constexpr since c++20
67
68 // 20.7.2.5, value status
69 constexpr bool valueless_by_exception() const noexcept;
70 constexpr size_t index() const noexcept;
71
72 // 20.7.2.6, swap
73 void swap(variant&) noexcept(see below);
74
75 // [variant.visit], visitation
76 template<class Self, class Visitor>
77 constexpr decltype(auto) visit(this Self&&, Visitor&&); // Since C++26
78 template<class R, class Self, class Visitor>
79 constexpr R visit(this Self&&, Visitor&&); // Since C++26
80 };
81
82 // 20.7.3, variant helper classes
83 template <class T> struct variant_size; // undefined
84
85 template <class T>
86 inline constexpr size_t variant_size_v = variant_size<T>::value;
87
88 template <class T> struct variant_size<const T>;
89 template <class T> struct variant_size<volatile T>;
90 template <class T> struct variant_size<const volatile T>;
91
92 template <class... Types>
93 struct variant_size<variant<Types...>>;
94
95 template <size_t I, class T> struct variant_alternative; // undefined
96
97 template <size_t I, class T>
98 using variant_alternative_t = typename variant_alternative<I, T>::type;
99
100 template <size_t I, class T> struct variant_alternative<I, const T>;
101 template <size_t I, class T> struct variant_alternative<I, volatile T>;
102 template <size_t I, class T> struct variant_alternative<I, const volatile T>;
103
104 template <size_t I, class... Types>
105 struct variant_alternative<I, variant<Types...>>;
106
107 inline constexpr size_t variant_npos = -1;
108
109 // 20.7.4, value access
110 template <class T, class... Types>
111 constexpr bool holds_alternative(const variant<Types...>&) noexcept;
112
113 template <size_t I, class... Types>
114 constexpr variant_alternative_t<I, variant<Types...>>&
115 get(variant<Types...>&);
116
117 template <size_t I, class... Types>
118 constexpr variant_alternative_t<I, variant<Types...>>&&
119 get(variant<Types...>&&);
120
121 template <size_t I, class... Types>
122 constexpr variant_alternative_t<I, variant<Types...>> const&
123 get(const variant<Types...>&);
124
125 template <size_t I, class... Types>
126 constexpr variant_alternative_t<I, variant<Types...>> const&&
127 get(const variant<Types...>&&);
128
129 template <class T, class... Types>
130 constexpr T& get(variant<Types...>&);
131
132 template <class T, class... Types>
133 constexpr T&& get(variant<Types...>&&);
134
135 template <class T, class... Types>
136 constexpr const T& get(const variant<Types...>&);
137
138 template <class T, class... Types>
139 constexpr const T&& get(const variant<Types...>&&);
140
141 template <size_t I, class... Types>
142 constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>>
143 get_if(variant<Types...>*) noexcept;
144
145 template <size_t I, class... Types>
146 constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>>
147 get_if(const variant<Types...>*) noexcept;
148
149 template <class T, class... Types>
150 constexpr add_pointer_t<T>
151 get_if(variant<Types...>*) noexcept;
152
153 template <class T, class... Types>
154 constexpr add_pointer_t<const T>
155 get_if(const variant<Types...>*) noexcept;
156
157 // 20.7.5, relational operators
158 template <class... Types>
159 constexpr bool operator==(const variant<Types...>&, const variant<Types...>&);
160
161 template <class... Types>
162 constexpr bool operator!=(const variant<Types...>&, const variant<Types...>&);
163
164 template <class... Types>
165 constexpr bool operator<(const variant<Types...>&, const variant<Types...>&);
166
167 template <class... Types>
168 constexpr bool operator>(const variant<Types...>&, const variant<Types...>&);
169
170 template <class... Types>
171 constexpr bool operator<=(const variant<Types...>&, const variant<Types...>&);
172
173 template <class... Types>
174 constexpr bool operator>=(const variant<Types...>&, const variant<Types...>&);
175
176 template <class... Types> requires (three_way_comparable<Types> && ...)
177 constexpr common_comparison_category_t<compare_three_way_result_t<Types>...>
178 operator<=>(const variant<Types...>&, const variant<Types...>&); // since C++20
179
180 // 20.7.6, visitation
181 template <class Visitor, class... Variants>
182 constexpr see below visit(Visitor&&, Variants&&...);
183
184 template <class R, class Visitor, class... Variants>
185 constexpr R visit(Visitor&&, Variants&&...); // since C++20
186
187 // 20.7.7, class monostate
188 struct monostate;
189
190 // 20.7.8, monostate relational operators
191 constexpr bool operator==(monostate, monostate) noexcept;
192 constexpr bool operator!=(monostate, monostate) noexcept; // until C++20
193 constexpr bool operator<(monostate, monostate) noexcept; // until C++20
194 constexpr bool operator>(monostate, monostate) noexcept; // until C++20
195 constexpr bool operator<=(monostate, monostate) noexcept; // until C++20
196 constexpr bool operator>=(monostate, monostate) noexcept; // until C++20
197 constexpr strong_ordering operator<=>(monostate, monostate) noexcept; // since C++20
198
199 // 20.7.9, specialized algorithms
200 template <class... Types>
201 void swap(variant<Types...>&, variant<Types...>&) noexcept(see below);
202
203 // 20.7.10, class bad_variant_access
204 class bad_variant_access;
205
206 // 20.7.11, hash support
207 template <class T> struct hash;
208 template <class... Types> struct hash<variant<Types...>>;
209 template <> struct hash<monostate>;
210
211} // namespace std
212
213*/
214
215#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
216# include <__cxx03/__config>
217#else
218# include <__compare/common_comparison_category.h>
219# include <__compare/compare_three_way_result.h>
220# include <__compare/ordering.h>
221# include <__compare/three_way_comparable.h>
222# include <__config>
223# include <__exception/exception.h>
224# include <__functional/hash.h>
225# include <__functional/operations.h>
226# include <__functional/unary_function.h>
227# include <__fwd/variant.h>
228# include <__memory/addressof.h>
229# include <__memory/construct_at.h>
230# include <__tuple/find_index.h>
231# include <__tuple/sfinae_helpers.h>
232# include <__type_traits/add_cv_quals.h>
233# include <__type_traits/add_pointer.h>
234# include <__type_traits/common_type.h>
235# include <__type_traits/conditional.h>
236# include <__type_traits/conjunction.h>
237# include <__type_traits/decay.h>
238# include <__type_traits/dependent_type.h>
239# include <__type_traits/enable_if.h>
240# include <__type_traits/invoke.h>
241# include <__type_traits/is_array.h>
242# include <__type_traits/is_assignable.h>
243# include <__type_traits/is_constructible.h>
244# include <__type_traits/is_convertible.h>
245# include <__type_traits/is_core_convertible.h>
246# include <__type_traits/is_destructible.h>
247# include <__type_traits/is_nothrow_assignable.h>
248# include <__type_traits/is_nothrow_constructible.h>
249# include <__type_traits/is_reference.h>
250# include <__type_traits/is_same.h>
251# include <__type_traits/is_swappable.h>
252# include <__type_traits/is_trivially_assignable.h>
253# include <__type_traits/is_trivially_constructible.h>
254# include <__type_traits/is_trivially_destructible.h>
255# include <__type_traits/is_trivially_relocatable.h>
256# include <__type_traits/is_void.h>
257# include <__type_traits/remove_const.h>
258# include <__type_traits/remove_cvref.h>
259# include <__type_traits/remove_reference.h>
260# include <__type_traits/type_identity.h>
261# include <__type_traits/void_t.h>
262# include <__utility/declval.h>
263# include <__utility/forward.h>
264# include <__utility/forward_like.h>
265# include <__utility/in_place.h>
266# include <__utility/integer_sequence.h>
267# include <__utility/move.h>
268# include <__utility/swap.h>
269# include <__variant/monostate.h>
270# include <__verbose_abort>
271# include <initializer_list>
272# include <limits>
273# include <version>
274
275// standard-mandated includes
276
277// [variant.syn]
278# include <compare>
279
280# if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
281# pragma GCC system_header
282# endif
283
284_LIBCPP_PUSH_MACROS
285# include <__undef_macros>
286
287_LIBCPP_BEGIN_UNVERSIONED_NAMESPACE_STD
288
289class _LIBCPP_EXPORTED_FROM_ABI bad_variant_access : public exception {
290public:
291 [[__nodiscard__]] const char* what() const _NOEXCEPT override;
292};
293
294_LIBCPP_END_UNVERSIONED_NAMESPACE_STD
295
296_LIBCPP_BEGIN_NAMESPACE_STD
297
298# if _LIBCPP_STD_VER >= 17
299
300// Light N-dimensional array of function pointers. Used in place of std::array to avoid
301// adding a dependency.
302template <class _Tp, size_t _Size>
303struct __farray {
304 static_assert(_Size > 0, "N-dimensional array should never be empty in std::visit");
305 _Tp __buf_[_Size] = {};
306
307 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp& operator[](size_t __n) const noexcept { return __buf_[__n]; }
308};
309
310[[noreturn]] inline _LIBCPP_HIDE_FROM_ABI void __throw_bad_variant_access() {
311# if _LIBCPP_HAS_EXCEPTIONS
312 throw bad_variant_access();
313# else
314 _LIBCPP_VERBOSE_ABORT("bad_variant_access was thrown in -fno-exceptions mode");
315# endif
316}
317
318// variant_size
319template <class _Tp>
320struct variant_size<const _Tp> : variant_size<_Tp> {};
321
322template <class _Tp>
323struct variant_size<volatile _Tp> : variant_size<_Tp> {};
324
325template <class _Tp>
326struct variant_size<const volatile _Tp> : variant_size<_Tp> {};
327
328template <class... _Types>
329struct variant_size<variant<_Types...>> : integral_constant<size_t, sizeof...(_Types)> {};
330
331// variant_alternative
332template <size_t _Ip, class _Tp>
333struct variant_alternative<_Ip, const _Tp> : add_const<variant_alternative_t<_Ip, _Tp>> {};
334
335template <size_t _Ip, class _Tp>
336struct variant_alternative<_Ip, volatile _Tp> : add_volatile<variant_alternative_t<_Ip, _Tp>> {};
337
338template <size_t _Ip, class _Tp>
339struct variant_alternative<_Ip, const volatile _Tp> : add_cv<variant_alternative_t<_Ip, _Tp>> {};
340
341template <size_t _Ip, class... _Types>
342struct variant_alternative<_Ip, variant<_Types...>> {
343 static_assert(_Ip < sizeof...(_Types), "Index out of bounds in std::variant_alternative<>");
344 using type _LIBCPP_NODEBUG = __type_pack_element<_Ip, _Types...>;
345};
346
347template <size_t _NumAlternatives>
348_LIBCPP_HIDE_FROM_ABI constexpr auto __choose_index_type() {
349# ifdef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
350 if constexpr (_NumAlternatives < numeric_limits<unsigned char>::max())
351 return static_cast<unsigned char>(0);
352 else if constexpr (_NumAlternatives < numeric_limits<unsigned short>::max())
353 return static_cast<unsigned short>(0);
354 else
355# endif // _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
356 return static_cast<unsigned int>(0);
357}
358
359template <size_t _NumAlts>
360using __variant_index_t _LIBCPP_NODEBUG = decltype(std::__choose_index_type<_NumAlts>());
361
362template <class _IndexType>
363constexpr _IndexType __variant_npos = static_cast<_IndexType>(-1);
364
365template <class... _Types>
366_LIBCPP_HIDE_FROM_ABI constexpr variant<_Types...>& __as_variant(variant<_Types...>& __vs) noexcept {
367 return __vs;
368}
369
370template <class... _Types>
371_LIBCPP_HIDE_FROM_ABI constexpr const variant<_Types...>& __as_variant(const variant<_Types...>& __vs) noexcept {
372 return __vs;
373}
374
375template <class... _Types>
376_LIBCPP_HIDE_FROM_ABI constexpr variant<_Types...>&& __as_variant(variant<_Types...>&& __vs) noexcept {
377 return std::move(__vs);
378}
379
380template <class... _Types>
381_LIBCPP_HIDE_FROM_ABI constexpr const variant<_Types...>&& __as_variant(const variant<_Types...>&& __vs) noexcept {
382 return std::move(__vs);
383}
384
385namespace __find_detail {
386
387template <class _Tp, class... _Types>
388_LIBCPP_HIDE_FROM_ABI constexpr size_t __find_index() {
389 constexpr bool __matches[] = {is_same_v<_Tp, _Types>...};
390 size_t __result = __not_found;
391 for (size_t __i = 0; __i < sizeof...(_Types); ++__i) {
392 if (__matches[__i]) {
393 if (__result != __not_found) {
394 return __ambiguous;
395 }
396 __result = __i;
397 }
398 }
399 return __result;
400}
401
402template <size_t _Index>
403struct __find_unambiguous_index_sfinae_impl : integral_constant<size_t, _Index> {};
404
405template <>
406struct __find_unambiguous_index_sfinae_impl<__not_found> {};
407
408template <>
409struct __find_unambiguous_index_sfinae_impl<__ambiguous> {};
410
411template <class _Tp, class... _Types>
412struct __find_unambiguous_index_sfinae
413 : __find_unambiguous_index_sfinae_impl<__find_detail::__find_index<_Tp, _Types...>()> {};
414
415} // namespace __find_detail
416
417namespace __variant_detail {
418
419struct __valueless_t {};
420
421enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
422
423template <typename _Tp, template <typename> class _IsTriviallyAvailable, template <typename> class _IsAvailable>
424constexpr _Trait __trait =
425 _IsTriviallyAvailable<_Tp>::value ? _Trait::_TriviallyAvailable
426 : _IsAvailable<_Tp>::value
427 ? _Trait::_Available
428 : _Trait::_Unavailable;
429
430_LIBCPP_HIDE_FROM_ABI constexpr _Trait __common_trait(initializer_list<_Trait> __traits) {
431 _Trait __result = _Trait::_TriviallyAvailable;
432 for (_Trait __t : __traits) {
433 if (static_cast<int>(__t) > static_cast<int>(__result)) {
434 __result = __t;
435 }
436 }
437 return __result;
438}
439
440template <typename... _Types>
441struct __traits {
442 static constexpr _Trait __copy_constructible_trait =
443 __variant_detail::__common_trait(traits: {__trait<_Types, is_trivially_copy_constructible, is_copy_constructible>...});
444
445 static constexpr _Trait __move_constructible_trait =
446 __variant_detail::__common_trait(traits: {__trait<_Types, is_trivially_move_constructible, is_move_constructible>...});
447
448 static constexpr _Trait __copy_assignable_trait = __variant_detail::__common_trait(
449 traits: {__copy_constructible_trait, __trait<_Types, is_trivially_copy_assignable, is_copy_assignable>...});
450
451 static constexpr _Trait __move_assignable_trait = __variant_detail::__common_trait(
452 traits: {__move_constructible_trait, __trait<_Types, is_trivially_move_assignable, is_move_assignable>...});
453
454 static constexpr _Trait __destructible_trait =
455 __variant_detail::__common_trait(traits: {__trait<_Types, is_trivially_destructible, is_destructible>...});
456};
457
458namespace __access {
459
460struct __union {
461 template <class _Vp>
462 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<0>) {
463 return std::forward<_Vp>(__v).__head;
464 }
465
466 template <class _Vp, size_t _Ip>
467 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<_Ip>) {
468 return __get_alt(std::forward<_Vp>(__v).__tail, in_place_index<_Ip - 1>);
469 }
470};
471
472struct __base {
473 template <size_t _Ip, class _Vp>
474 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v) {
475 return __union::__get_alt(std::forward<_Vp>(__v).__data, in_place_index<_Ip>);
476 }
477};
478
479struct __variant {
480 template <size_t _Ip, class _Vp>
481 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v) {
482 return __base::__get_alt<_Ip>(std::forward<_Vp>(__v).__impl_);
483 }
484};
485
486} // namespace __access
487
488namespace __visitation {
489
490struct __base {
491 template <class _Visitor, class... _Vs>
492 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto)
493 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
494 constexpr auto __fdiagonal = __make_fdiagonal<_Visitor&&, decltype(std::forward<_Vs>(__vs).__as_base())...>();
495 return __fdiagonal[__index](std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs).__as_base()...);
496 }
497
498 template <class _Visitor, class... _Vs>
499 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor, _Vs&&... __vs) {
500 constexpr auto __fmatrix = __make_fmatrix<_Visitor&&, decltype(std::forward<_Vs>(__vs).__as_base())...>();
501 return __at(__fmatrix, __vs.index()...)(std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs).__as_base()...);
502 }
503
504private:
505 template <class _Tp>
506 _LIBCPP_HIDE_FROM_ABI static constexpr const _Tp& __at(const _Tp& __elem) {
507 return __elem;
508 }
509
510 template <class _Tp, size_t _Np, typename... _Indices>
511 _LIBCPP_HIDE_FROM_ABI static constexpr auto&&
512 __at(const __farray<_Tp, _Np>& __elems, size_t __index, _Indices... __indices) {
513 return __at(__elems[__index], __indices...);
514 }
515
516 template <class _Fp, class... _Fs>
517 static _LIBCPP_HIDE_FROM_ABI constexpr void __std_visit_visitor_return_type_check() {
518 static_assert(
519 __all<is_same_v<_Fp, _Fs>...>::value, "`std::visit` requires the visitor to have a single return type.");
520 }
521
522 template <class... _Fs>
523 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_farray(_Fs&&... __fs) {
524 __std_visit_visitor_return_type_check<__remove_cvref_t<_Fs>...>();
525 using __result = __farray<common_type_t<__remove_cvref_t<_Fs>...>, sizeof...(_Fs)>;
526 return __result{{std::forward<_Fs>(__fs)...}};
527 }
528
529 template <size_t... _Is>
530 struct __dispatcher {
531 template <class _Fp, class... _Vs>
532 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
533 return std::__invoke(static_cast<_Fp>(__f), __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
534 }
535 };
536
537 template <class _Fp, class... _Vs, size_t... _Is>
538 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_dispatch(index_sequence<_Is...>) {
539 return __dispatcher<_Is...>::template __dispatch<_Fp, _Vs...>;
540 }
541
542 template <size_t _Ip, class _Fp, class... _Vs>
543 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fdiagonal_impl() {
544 return __make_dispatch<_Fp, _Vs...>(index_sequence<((void)__type_identity<_Vs>{}, _Ip)...>{});
545 }
546
547 template <class _Fp, class... _Vs, size_t... _Is>
548 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
549 return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
550 }
551
552 template <class _Fp, class _Vp, class... _Vs>
553 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fdiagonal() {
554 constexpr size_t __np = __remove_cvref_t<_Vp>::__size();
555 static_assert(__all<(__np == __remove_cvref_t<_Vs>::__size())...>::value);
556 return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<__np>{});
557 }
558
559 template <class _Fp, class... _Vs, size_t... _Is>
560 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
561 return __make_dispatch<_Fp, _Vs...>(__is);
562 }
563
564 template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
565 _LIBCPP_HIDE_FROM_ABI static constexpr auto
566 __make_fmatrix_impl(index_sequence<_Is...>, index_sequence<_Js...>, _Ls... __ls) {
567 return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(index_sequence<_Is..., _Js>{}, __ls...)...);
568 }
569
570 template <class _Fp, class... _Vs>
571 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fmatrix() {
572 return __make_fmatrix_impl<_Fp, _Vs...>(
573 index_sequence<>{}, make_index_sequence<__remove_cvref_t<_Vs>::__size()>{}...);
574 }
575};
576
577struct __variant {
578 template <class _Visitor, class... _Vs>
579 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto)
580 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
581 return __base::__visit_alt_at(__index, std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs).__impl_...);
582 }
583
584 template <class _Visitor, class... _Vs>
585 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor, _Vs&&... __vs) {
586 return __base::__visit_alt(
587 std::forward<_Visitor>(__visitor), std::__as_variant(std::forward<_Vs>(__vs)).__impl_...);
588 }
589
590 template <class _Visitor, class... _Vs>
591 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto)
592 __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
593 return __visit_alt_at(__index, __make_value_visitor(std::forward<_Visitor>(__visitor)), std::forward<_Vs>(__vs)...);
594 }
595
596 template <class _Visitor, class... _Vs>
597 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __visit_value(_Visitor&& __visitor, _Vs&&... __vs) {
598 return __visit_alt(__make_value_visitor(std::forward<_Visitor>(__visitor)), std::forward<_Vs>(__vs)...);
599 }
600
601# if _LIBCPP_STD_VER >= 20
602 template <class _Rp, class _Visitor, class... _Vs>
603 _LIBCPP_HIDE_FROM_ABI static constexpr _Rp __visit_value(_Visitor&& __visitor, _Vs&&... __vs) {
604 return __visit_alt(__make_value_visitor<_Rp>(std::forward<_Visitor>(__visitor)), std::forward<_Vs>(__vs)...);
605 }
606# endif
607
608private:
609 template <class _Visitor, class... _Values>
610 static _LIBCPP_HIDE_FROM_ABI constexpr void __std_visit_exhaustive_visitor_check() {
611 static_assert(is_invocable_v<_Visitor, _Values...>, "`std::visit` requires the visitor to be exhaustive.");
612 }
613
614 template <class _Visitor>
615 struct __value_visitor {
616 template <class... _Alts>
617 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Alts&&... __alts) const
618 -> invoke_result_t<_Visitor&&, decltype((std::forward<_Alts>(__alts).__value))...> {
619 __std_visit_exhaustive_visitor_check< _Visitor, decltype((std::forward<_Alts>(__alts).__value))...>();
620 return std::__invoke(std::forward<_Visitor>(__visitor), std::forward<_Alts>(__alts).__value...);
621 }
622 _Visitor&& __visitor;
623 };
624
625# if _LIBCPP_STD_VER >= 20
626 template <class _Rp, class _Visitor>
627 struct __value_visitor_return_type {
628 template <class... _Alts>
629 _LIBCPP_HIDE_FROM_ABI constexpr _Rp operator()(_Alts&&... __alts) const {
630 __std_visit_exhaustive_visitor_check< _Visitor, decltype((std::forward<_Alts>(__alts).__value))...>();
631 if constexpr (is_void_v<_Rp>) {
632 std::__invoke(std::forward<_Visitor>(__visitor), std::forward<_Alts>(__alts).__value...);
633 } else {
634 return std::__invoke(std::forward<_Visitor>(__visitor), std::forward<_Alts>(__alts).__value...);
635 }
636 }
637
638 _Visitor&& __visitor;
639 };
640# endif
641
642 template <class _Visitor>
643 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
644 return __value_visitor<_Visitor>{std::forward<_Visitor>(__visitor)};
645 }
646
647# if _LIBCPP_STD_VER >= 20
648 template <class _Rp, class _Visitor>
649 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
650 return __value_visitor_return_type<_Rp, _Visitor>{std::forward<_Visitor>(__visitor)};
651 }
652# endif
653};
654
655} // namespace __visitation
656
657// Adding semi-colons in macro expansions helps clang-format to do a better job.
658// This macro is used to avoid compilation errors due to "stray" semi-colons.
659# define _LIBCPP_EAT_SEMICOLON static_assert(true, "")
660
661template <size_t _Index, class _Tp>
662struct __alt {
663 using __value_type _LIBCPP_NODEBUG = _Tp;
664 static constexpr size_t __index = _Index;
665
666 template <class... _Args>
667 _LIBCPP_HIDE_FROM_ABI explicit constexpr __alt(in_place_t, _Args&&... __args)
668 : __value(std::forward<_Args>(__args)...) {}
669
670 __value_type __value;
671};
672
673template <_Trait _DestructibleTrait, size_t _Index, class... _Types>
674union __union;
675
676template <_Trait _DestructibleTrait, size_t _Index>
677union __union<_DestructibleTrait, _Index> {};
678
679# define _LIBCPP_VARIANT_UNION(destructible_trait, destructor_definition) \
680 template <size_t _Index, class _Tp, class... _Types> \
681 union __union<destructible_trait, _Index, _Tp, _Types...> { \
682 public: \
683 _LIBCPP_HIDE_FROM_ABI explicit constexpr __union(__valueless_t) noexcept : __dummy{} {} \
684 \
685 template <class... _Args> \
686 _LIBCPP_HIDE_FROM_ABI explicit constexpr __union(in_place_index_t<0>, _Args&&... __args) \
687 : __head(in_place, std::forward<_Args>(__args)...) {} \
688 \
689 template <size_t _Ip, class... _Args> \
690 _LIBCPP_HIDE_FROM_ABI explicit constexpr __union(in_place_index_t<_Ip>, _Args&&... __args) \
691 : __tail(in_place_index<_Ip - 1>, std::forward<_Args>(__args)...) {} \
692 \
693 _LIBCPP_HIDE_FROM_ABI __union(const __union&) = default; \
694 _LIBCPP_HIDE_FROM_ABI __union(__union&&) = default; \
695 _LIBCPP_HIDE_FROM_ABI __union& operator=(const __union&) = default; \
696 _LIBCPP_HIDE_FROM_ABI __union& operator=(__union&&) = default; \
697 destructor_definition; \
698 \
699 private: \
700 char __dummy; \
701 __alt<_Index, _Tp> __head; \
702 __union<destructible_trait, _Index + 1, _Types...> __tail; \
703 \
704 friend struct __access::__union; \
705 }
706
707_LIBCPP_VARIANT_UNION(_Trait::_TriviallyAvailable,
708 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__union() = default);
709_LIBCPP_VARIANT_UNION(
710 _Trait::_Available, _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__union() {} _LIBCPP_EAT_SEMICOLON);
711_LIBCPP_VARIANT_UNION(_Trait::_Unavailable, _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__union() = delete);
712
713# undef _LIBCPP_VARIANT_UNION
714
715template <_Trait _DestructibleTrait, class... _Types>
716class __base {
717public:
718 using __index_t _LIBCPP_NODEBUG = __variant_index_t<sizeof...(_Types)>;
719
720 _LIBCPP_HIDE_FROM_ABI explicit constexpr __base(__valueless_t __tag) noexcept
721 : __data(__tag), __index(__variant_npos<__index_t>) {}
722
723 template <size_t _Ip, class... _Args>
724 _LIBCPP_HIDE_FROM_ABI explicit constexpr __base(in_place_index_t<_Ip>, _Args&&... __args)
725 : __data(in_place_index<_Ip>, std::forward<_Args>(__args)...), __index(_Ip) {}
726
727 _LIBCPP_HIDE_FROM_ABI constexpr bool valueless_by_exception() const noexcept { return index() == variant_npos; }
728
729 _LIBCPP_HIDE_FROM_ABI constexpr size_t index() const noexcept {
730 return __index == __variant_npos<__index_t> ? variant_npos : __index;
731 }
732
733protected:
734 _LIBCPP_HIDE_FROM_ABI constexpr auto&& __as_base() & { return *this; }
735
736 _LIBCPP_HIDE_FROM_ABI constexpr auto&& __as_base() && { return std::move(*this); }
737
738 _LIBCPP_HIDE_FROM_ABI constexpr auto&& __as_base() const& { return *this; }
739
740 _LIBCPP_HIDE_FROM_ABI constexpr auto&& __as_base() const&& { return std::move(*this); }
741
742 _LIBCPP_HIDE_FROM_ABI static constexpr size_t __size() { return sizeof...(_Types); }
743
744 __union<_DestructibleTrait, 0, _Types...> __data;
745 __index_t __index;
746
747 friend struct __access::__base;
748 friend struct __visitation::__base;
749};
750
751template <class _Traits, _Trait = _Traits::__destructible_trait>
752class __dtor;
753
754# define _LIBCPP_VARIANT_DESTRUCTOR(destructible_trait, destructor_definition, destroy) \
755 template <class... _Types> \
756 class __dtor<__traits<_Types...>, destructible_trait> : public __base<destructible_trait, _Types...> { \
757 using __base_type _LIBCPP_NODEBUG = __base<destructible_trait, _Types...>; \
758 using __index_t _LIBCPP_NODEBUG = typename __base_type::__index_t; \
759 \
760 public: \
761 using __base_type::__base_type; \
762 using __base_type::operator=; \
763 _LIBCPP_HIDE_FROM_ABI __dtor(const __dtor&) = default; \
764 _LIBCPP_HIDE_FROM_ABI __dtor(__dtor&&) = default; \
765 _LIBCPP_HIDE_FROM_ABI __dtor& operator=(const __dtor&) = default; \
766 _LIBCPP_HIDE_FROM_ABI __dtor& operator=(__dtor&&) = default; \
767 destructor_definition; \
768 \
769 protected: \
770 destroy; \
771 }
772
773_LIBCPP_VARIANT_DESTRUCTOR(
774 _Trait::_TriviallyAvailable,
775 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__dtor() = default,
776 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __destroy() noexcept {
777 this->__index = __variant_npos<__index_t>;
778 } _LIBCPP_EAT_SEMICOLON);
779
780_LIBCPP_VARIANT_DESTRUCTOR(
781 _Trait::_Available,
782 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__dtor() { __destroy(); } _LIBCPP_EAT_SEMICOLON,
783 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __destroy() noexcept {
784 if (!this->valueless_by_exception()) {
785 __visitation::__base::__visit_alt(
786 [](auto& __alt) noexcept {
787 using __alt_type = __remove_cvref_t<decltype(__alt)>;
788 __alt.~__alt_type();
789 },
790 *this);
791 }
792 this->__index = __variant_npos<__index_t>;
793 } _LIBCPP_EAT_SEMICOLON);
794
795_LIBCPP_VARIANT_DESTRUCTOR(_Trait::_Unavailable,
796 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__dtor() = delete,
797 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __destroy() noexcept = delete);
798
799# undef _LIBCPP_VARIANT_DESTRUCTOR
800
801template <class _Traits>
802class __ctor : public __dtor<_Traits> {
803 using __base_type _LIBCPP_NODEBUG = __dtor<_Traits>;
804
805public:
806 using __base_type::__base_type;
807 using __base_type::operator=;
808
809protected:
810 template <class _Rhs>
811 _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR_SINCE_CXX20 void __generic_construct(__ctor& __lhs, _Rhs&& __rhs) {
812 __lhs.__destroy();
813 if (!__rhs.valueless_by_exception()) {
814 auto __rhs_index = __rhs.index();
815 __visitation::__base::__visit_alt_at(
816 __rhs_index,
817 [&__lhs](auto&& __rhs_alt) {
818 std::__construct_at(std::addressof(__lhs.__data),
819 in_place_index<__decay_t<decltype(__rhs_alt)>::__index>,
820 std::forward<decltype(__rhs_alt)>(__rhs_alt).__value);
821 },
822 std::forward<_Rhs>(__rhs));
823 __lhs.__index = __rhs_index;
824 }
825 }
826};
827
828template <class _Traits, _Trait = _Traits::__move_constructible_trait>
829class __move_constructor;
830
831# define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, move_constructor_definition) \
832 template <class... _Types> \
833 class __move_constructor<__traits<_Types...>, move_constructible_trait> : public __ctor<__traits<_Types...>> { \
834 using __base_type _LIBCPP_NODEBUG = __ctor<__traits<_Types...>>; \
835 \
836 public: \
837 using __base_type::__base_type; \
838 using __base_type::operator=; \
839 \
840 _LIBCPP_HIDE_FROM_ABI __move_constructor(const __move_constructor&) = default; \
841 _LIBCPP_HIDE_FROM_ABI ~__move_constructor() = default; \
842 _LIBCPP_HIDE_FROM_ABI __move_constructor& operator=(const __move_constructor&) = default; \
843 _LIBCPP_HIDE_FROM_ABI __move_constructor& operator=(__move_constructor&&) = default; \
844 move_constructor_definition; \
845 }
846
847_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
848 _Trait::_TriviallyAvailable,
849 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_constructor(__move_constructor&& __that) = default);
850
851_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
852 _Trait::_Available,
853 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_constructor(__move_constructor&& __that) noexcept(
854 __all<is_nothrow_move_constructible_v<_Types>...>::value) : __move_constructor(__valueless_t{}) {
855 this->__generic_construct(*this, std::move(__that));
856 } _LIBCPP_EAT_SEMICOLON);
857
858_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
859 _Trait::_Unavailable,
860 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_constructor(__move_constructor&&) = delete);
861
862# undef _LIBCPP_VARIANT_MOVE_CONSTRUCTOR
863
864template <class _Traits, _Trait = _Traits::__copy_constructible_trait>
865class __copy_constructor;
866
867# define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, copy_constructor_definition) \
868 template <class... _Types> \
869 class __copy_constructor<__traits<_Types...>, copy_constructible_trait> \
870 : public __move_constructor<__traits<_Types...>> { \
871 using __base_type _LIBCPP_NODEBUG = __move_constructor<__traits<_Types...>>; \
872 \
873 public: \
874 using __base_type::__base_type; \
875 using __base_type::operator=; \
876 \
877 _LIBCPP_HIDE_FROM_ABI __copy_constructor(__copy_constructor&&) = default; \
878 _LIBCPP_HIDE_FROM_ABI ~__copy_constructor() = default; \
879 _LIBCPP_HIDE_FROM_ABI __copy_constructor& operator=(const __copy_constructor&) = default; \
880 _LIBCPP_HIDE_FROM_ABI __copy_constructor& operator=(__copy_constructor&&) = default; \
881 copy_constructor_definition; \
882 }
883
884_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
885 _Trait::_TriviallyAvailable,
886 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_constructor(const __copy_constructor& __that) = default);
887
888_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
889 _Trait::_Available,
890 _LIBCPP_HIDE_FROM_ABI
891 _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_constructor(const __copy_constructor& __that) : __copy_constructor(
892 __valueless_t{}) { this->__generic_construct(*this, __that); } _LIBCPP_EAT_SEMICOLON);
893
894_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
895 _Trait::_Unavailable,
896 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_constructor(const __copy_constructor&) = delete);
897
898# undef _LIBCPP_VARIANT_COPY_CONSTRUCTOR
899
900template <class _Traits>
901class __assignment : public __copy_constructor<_Traits> {
902 using __base_type _LIBCPP_NODEBUG = __copy_constructor<_Traits>;
903
904public:
905 using __base_type::__base_type;
906 using __base_type::operator=;
907
908 template <size_t _Ip, class... _Args>
909 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 auto& __emplace(_Args&&... __args) {
910 this->__destroy();
911 std::__construct_at(std::addressof(this->__data), in_place_index<_Ip>, std::forward<_Args>(__args)...);
912 this->__index = _Ip;
913 return __access::__base::__get_alt<_Ip>(*this).__value;
914 }
915
916protected:
917 template <size_t _Ip, class _Tp, class _Arg>
918 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __assign_alt(__alt<_Ip, _Tp>& __a, _Arg&& __arg) {
919 if (this->index() == _Ip) {
920 __a.__value = std::forward<_Arg>(__arg);
921 } else if constexpr (is_nothrow_constructible_v<_Tp, _Arg> || !is_nothrow_move_constructible_v<_Tp>) {
922 this->__emplace<_Ip>(std::forward<_Arg>(__arg));
923 } else {
924 this->__emplace<_Ip>(_Tp(std::forward<_Arg>(__arg)));
925 }
926 }
927
928 template <class _That>
929 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __generic_assign(_That&& __that) {
930 if (this->valueless_by_exception() && __that.valueless_by_exception()) {
931 // do nothing.
932 } else if (__that.valueless_by_exception()) {
933 this->__destroy();
934 } else {
935 __visitation::__base::__visit_alt_at(
936 __that.index(),
937 [this](auto& __this_alt, auto&& __that_alt) {
938 this->__assign_alt(__this_alt, std::forward<decltype(__that_alt)>(__that_alt).__value);
939 },
940 *this,
941 std::forward<_That>(__that));
942 }
943 }
944};
945
946template <class _Traits, _Trait = _Traits::__move_assignable_trait>
947class __move_assignment;
948
949# define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, move_assignment_definition) \
950 template <class... _Types> \
951 class __move_assignment<__traits<_Types...>, move_assignable_trait> : public __assignment<__traits<_Types...>> { \
952 using __base_type _LIBCPP_NODEBUG = __assignment<__traits<_Types...>>; \
953 \
954 public: \
955 using __base_type::__base_type; \
956 using __base_type::operator=; \
957 \
958 _LIBCPP_HIDE_FROM_ABI __move_assignment(const __move_assignment&) = default; \
959 _LIBCPP_HIDE_FROM_ABI __move_assignment(__move_assignment&&) = default; \
960 _LIBCPP_HIDE_FROM_ABI ~__move_assignment() = default; \
961 _LIBCPP_HIDE_FROM_ABI __move_assignment& operator=(const __move_assignment&) = default; \
962 move_assignment_definition; \
963 }
964
965_LIBCPP_VARIANT_MOVE_ASSIGNMENT(_Trait::_TriviallyAvailable,
966 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_assignment& operator=(
967 __move_assignment&& __that) = default);
968
969_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
970 _Trait::_Available,
971 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_assignment&
972 operator=(__move_assignment&& __that) noexcept(
973 __all<(is_nothrow_move_constructible_v<_Types> && is_nothrow_move_assignable_v<_Types>)...>::value) {
974 this->__generic_assign(std::move(__that));
975 return *this;
976 } _LIBCPP_EAT_SEMICOLON);
977
978_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
979 _Trait::_Unavailable,
980 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_assignment& operator=(__move_assignment&&) = delete);
981
982# undef _LIBCPP_VARIANT_MOVE_ASSIGNMENT
983
984template <class _Traits, _Trait = _Traits::__copy_assignable_trait>
985class __copy_assignment;
986
987# define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, copy_assignment_definition) \
988 template <class... _Types> \
989 class __copy_assignment<__traits<_Types...>, copy_assignable_trait> \
990 : public __move_assignment<__traits<_Types...>> { \
991 using __base_type _LIBCPP_NODEBUG = __move_assignment<__traits<_Types...>>; \
992 \
993 public: \
994 using __base_type::__base_type; \
995 using __base_type::operator=; \
996 \
997 _LIBCPP_HIDE_FROM_ABI __copy_assignment(const __copy_assignment&) = default; \
998 _LIBCPP_HIDE_FROM_ABI __copy_assignment(__copy_assignment&&) = default; \
999 _LIBCPP_HIDE_FROM_ABI ~__copy_assignment() = default; \
1000 _LIBCPP_HIDE_FROM_ABI __copy_assignment& operator=(__copy_assignment&&) = default; \
1001 copy_assignment_definition; \
1002 }
1003
1004_LIBCPP_VARIANT_COPY_ASSIGNMENT(_Trait::_TriviallyAvailable,
1005 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_assignment& operator=(
1006 const __copy_assignment& __that) = default);
1007
1008_LIBCPP_VARIANT_COPY_ASSIGNMENT(
1009 _Trait::_Available,
1010 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_assignment&
1011 operator=(const __copy_assignment& __that) {
1012 this->__generic_assign(__that);
1013 return *this;
1014 } _LIBCPP_EAT_SEMICOLON);
1015
1016_LIBCPP_VARIANT_COPY_ASSIGNMENT(_Trait::_Unavailable,
1017 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_assignment& operator=(
1018 const __copy_assignment&) = delete);
1019
1020# undef _LIBCPP_VARIANT_COPY_ASSIGNMENT
1021
1022template <class... _Types>
1023class __impl : public __copy_assignment<__traits<_Types...>> {
1024 using __base_type _LIBCPP_NODEBUG = __copy_assignment<__traits<_Types...>>;
1025
1026public:
1027 using __base_type::__base_type; // get in_place_index_t constructor & friends
1028 _LIBCPP_HIDE_FROM_ABI __impl(__impl const&) = default;
1029 _LIBCPP_HIDE_FROM_ABI __impl(__impl&&) = default;
1030 _LIBCPP_HIDE_FROM_ABI __impl& operator=(__impl const&) = default;
1031 _LIBCPP_HIDE_FROM_ABI __impl& operator=(__impl&&) = default;
1032
1033 template <size_t _Ip, class _Arg>
1034 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __assign(_Arg&& __arg) {
1035 this->__assign_alt(__access::__base::__get_alt<_Ip>(*this), std::forward<_Arg>(__arg));
1036 }
1037
1038 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __swap(__impl& __that) {
1039 if (this->valueless_by_exception() && __that.valueless_by_exception()) {
1040 // do nothing.
1041 } else if (this->index() == __that.index()) {
1042 __visitation::__base::__visit_alt_at(
1043 this->index(),
1044 [](auto& __this_alt, auto& __that_alt) {
1045 using std::swap;
1046 swap(__this_alt.__value, __that_alt.__value);
1047 },
1048 *this,
1049 __that);
1050 } else {
1051 __impl* __lhs = this;
1052 __impl* __rhs = std::addressof(__that);
1053 if (__lhs->__move_nothrow() && !__rhs->__move_nothrow()) {
1054 std::swap(__lhs, __rhs);
1055 }
1056 __impl __tmp(std::move(*__rhs));
1057# if _LIBCPP_HAS_EXCEPTIONS
1058 if constexpr (__all<is_nothrow_move_constructible_v<_Types>...>::value) {
1059 this->__generic_construct(*__rhs, std::move(*__lhs));
1060 } else {
1061 // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
1062 // and `__tmp` is nothrow move constructible then we move `__tmp` back
1063 // into `__rhs` and provide the strong exception safety guarantee.
1064 try {
1065 this->__generic_construct(*__rhs, std::move(*__lhs));
1066 } catch (...) {
1067 if (__tmp.__move_nothrow()) {
1068 this->__generic_construct(*__rhs, std::move(__tmp));
1069 }
1070 throw;
1071 }
1072 }
1073# else
1074 // this isn't consolidated with the `if constexpr` branch above due to
1075 // `throw` being ill-formed with exceptions disabled even when discarded.
1076 this->__generic_construct(*__rhs, std::move(*__lhs));
1077# endif
1078 this->__generic_construct(*__lhs, std::move(__tmp));
1079 }
1080 }
1081
1082private:
1083 constexpr inline _LIBCPP_HIDE_FROM_ABI bool __move_nothrow() const {
1084 constexpr bool __results[] = {is_nothrow_move_constructible_v<_Types>...};
1085 return this->valueless_by_exception() || __results[this->index()];
1086 }
1087};
1088
1089struct __no_narrowing_check {
1090 template <class _Dest, class _Source>
1091 using _Apply _LIBCPP_NODEBUG = __type_identity<_Dest>;
1092};
1093
1094struct __narrowing_check {
1095 template <class _Dest>
1096 static auto __test_impl(_Dest (&&)[1]) -> __type_identity<_Dest>;
1097 template <class _Dest, class _Source>
1098 using _Apply _LIBCPP_NODEBUG = decltype(__test_impl<_Dest>({std::declval<_Source>()}));
1099};
1100
1101template <class _Dest, class _Source>
1102using __check_for_narrowing _LIBCPP_NODEBUG =
1103 typename _If< is_arithmetic<_Dest>::value, __narrowing_check, __no_narrowing_check >::template _Apply<_Dest,
1104 _Source>;
1105
1106template <class _Tp, size_t _Idx>
1107struct __overload {
1108 template <class _Up>
1109 auto operator()(_Tp, _Up&&) const -> __check_for_narrowing<_Tp, _Up>;
1110};
1111
1112template <class... _Bases>
1113struct __all_overloads : _Bases... {
1114 void operator()() const;
1115 using _Bases::operator()...;
1116};
1117
1118template <class _IdxSeq>
1119struct __make_overloads_imp;
1120
1121template <size_t... _Idx>
1122struct __make_overloads_imp<index_sequence<_Idx...> > {
1123 template <class... _Types>
1124 using _Apply _LIBCPP_NODEBUG = __all_overloads<__overload<_Types, _Idx>...>;
1125};
1126
1127template <class... _Types>
1128using _MakeOverloads _LIBCPP_NODEBUG =
1129 typename __make_overloads_imp<make_index_sequence<sizeof...(_Types)>>::template _Apply<_Types...>;
1130
1131template <class _Tp, class... _Types>
1132using __best_match_t _LIBCPP_NODEBUG = typename invoke_result_t<_MakeOverloads<_Types...>, _Tp, _Tp>::type;
1133
1134} // namespace __variant_detail
1135
1136template <class _Visitor, class... _Vs, typename = void_t<decltype(std::__as_variant(std::declval<_Vs>()))...>>
1137_LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs);
1138
1139# if _LIBCPP_STD_VER >= 20
1140template <class _Rp,
1141 class _Visitor,
1142 class... _Vs,
1143 typename = void_t<decltype(std::__as_variant(std::declval<_Vs>()))...>>
1144_LIBCPP_HIDE_FROM_ABI constexpr _Rp visit(_Visitor&& __visitor, _Vs&&... __vs);
1145# endif
1146
1147template <class... _Types>
1148class _LIBCPP_DECLSPEC_EMPTY_BASES _LIBCPP_NO_SPECIALIZATIONS variant
1149 : private __sfinae_ctor_base< __all<is_copy_constructible_v<_Types>...>::value,
1150 __all<is_move_constructible_v<_Types>...>::value>,
1151 private __sfinae_assign_base<
1152 __all<(is_copy_constructible_v<_Types> && is_copy_assignable_v<_Types>)...>::value,
1153 __all<(is_move_constructible_v<_Types> && is_move_assignable_v<_Types>)...>::value> {
1154 static_assert(0 < sizeof...(_Types), "variant must consist of at least one alternative.");
1155
1156 static_assert(__all<!is_array_v<_Types>...>::value, "variant can not have an array type as an alternative.");
1157
1158 static_assert(__all<!is_reference_v<_Types>...>::value, "variant can not have a reference type as an alternative.");
1159
1160 static_assert(__all<!is_void_v<_Types>...>::value, "variant can not have a void type as an alternative.");
1161
1162 using __first_type _LIBCPP_NODEBUG = variant_alternative_t<0, variant>;
1163
1164public:
1165 using __trivially_relocatable _LIBCPP_NODEBUG =
1166 conditional_t<_And<__libcpp_is_trivially_relocatable<_Types>...>::value, variant, void>;
1167
1168 template <bool _Dummy = true,
1169 enable_if_t<__dependent_type<is_default_constructible<__first_type>, _Dummy>::value, int> = 0>
1170 _LIBCPP_HIDE_FROM_ABI constexpr variant() noexcept(is_nothrow_default_constructible_v<__first_type>)
1171 : __impl_(in_place_index<0>) {}
1172
1173 _LIBCPP_HIDE_FROM_ABI constexpr variant(const variant&) = default;
1174 _LIBCPP_HIDE_FROM_ABI constexpr variant(variant&&) = default;
1175
1176 template < class _Arg,
1177 enable_if_t<!is_same_v<__remove_cvref_t<_Arg>, variant>, int> = 0,
1178 enable_if_t<!__is_inplace_type<__remove_cvref_t<_Arg>>::value, int> = 0,
1179 enable_if_t<!__is_inplace_index<__remove_cvref_t<_Arg>>::value, int> = 0,
1180 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1181 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1182 enable_if_t<is_constructible_v<_Tp, _Arg>, int> = 0>
1183 _LIBCPP_HIDE_FROM_ABI constexpr variant(_Arg&& __arg) noexcept(is_nothrow_constructible_v<_Tp, _Arg>)
1184 : __impl_(in_place_index<_Ip>, std::forward<_Arg>(__arg)) {}
1185
1186 template <size_t _Ip,
1187 class... _Args,
1188 class = enable_if_t<(_Ip < sizeof...(_Types)), int>,
1189 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1190 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1191 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(in_place_index_t<_Ip>, _Args&&... __args) noexcept(
1192 is_nothrow_constructible_v<_Tp, _Args...>)
1193 : __impl_(in_place_index<_Ip>, std::forward<_Args>(__args)...) {}
1194
1195 template < size_t _Ip,
1196 class _Up,
1197 class... _Args,
1198 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1199 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1200 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1201 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(
1202 in_place_index_t<_Ip>,
1203 initializer_list<_Up> __il,
1204 _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
1205 : __impl_(in_place_index<_Ip>, __il, std::forward<_Args>(__args)...) {}
1206
1207 template < class _Tp,
1208 class... _Args,
1209 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1210 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1211 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(in_place_type_t<_Tp>, _Args&&... __args) noexcept(
1212 is_nothrow_constructible_v<_Tp, _Args...>)
1213 : __impl_(in_place_index<_Ip>, std::forward<_Args>(__args)...) {}
1214
1215 template < class _Tp,
1216 class _Up,
1217 class... _Args,
1218 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1219 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1220 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(
1221 in_place_type_t<_Tp>,
1222 initializer_list<_Up> __il,
1223 _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, initializer_list< _Up>&, _Args...>)
1224 : __impl_(in_place_index<_Ip>, __il, std::forward<_Args>(__args)...) {}
1225
1226 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~variant() = default;
1227
1228 _LIBCPP_HIDE_FROM_ABI constexpr variant& operator=(const variant&) = default;
1229 _LIBCPP_HIDE_FROM_ABI constexpr variant& operator=(variant&&) = default;
1230
1231 template < class _Arg,
1232 enable_if_t<!is_same_v<__remove_cvref_t<_Arg>, variant>, int> = 0,
1233 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1234 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1235 enable_if_t<is_assignable_v<_Tp&, _Arg> && is_constructible_v<_Tp, _Arg>, int> = 0>
1236 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 variant&
1237 operator=(_Arg&& __arg) noexcept(is_nothrow_assignable_v<_Tp&, _Arg> && is_nothrow_constructible_v<_Tp, _Arg>) {
1238 __impl_.template __assign<_Ip>(std::forward<_Arg>(__arg));
1239 return *this;
1240 }
1241
1242 template < size_t _Ip,
1243 class... _Args,
1244 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1245 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1246 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1247 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(_Args&&... __args) {
1248 return __impl_.template __emplace<_Ip>(std::forward<_Args>(__args)...);
1249 }
1250
1251 template < size_t _Ip,
1252 class _Up,
1253 class... _Args,
1254 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1255 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1256 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1257 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1258 return __impl_.template __emplace<_Ip>(__il, std::forward<_Args>(__args)...);
1259 }
1260
1261 template < class _Tp,
1262 class... _Args,
1263 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1264 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1265 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(_Args&&... __args) {
1266 return __impl_.template __emplace<_Ip>(std::forward<_Args>(__args)...);
1267 }
1268
1269 template < class _Tp,
1270 class _Up,
1271 class... _Args,
1272 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1273 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1274 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1275 return __impl_.template __emplace<_Ip>(__il, std::forward<_Args>(__args)...);
1276 }
1277
1278 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool valueless_by_exception() const noexcept {
1279 return __impl_.valueless_by_exception();
1280 }
1281
1282 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t index() const noexcept { return __impl_.index(); }
1283
1284 template < bool _Dummy = true,
1285 enable_if_t< __all<(__dependent_type<is_move_constructible<_Types>, _Dummy>::value &&
1286 __dependent_type<is_swappable<_Types>, _Dummy>::value)...>::value,
1287 int> = 0>
1288 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void swap(variant& __that) noexcept(
1289 __all<(is_nothrow_move_constructible_v<_Types> && is_nothrow_swappable_v<_Types>)...>::value) {
1290 __impl_.__swap(__that.__impl_);
1291 }
1292
1293# if _LIBCPP_STD_VER >= 26
1294 // Helper class to implement [variant.visit]/10
1295 // Constraints: The call to visit does not use an explicit template-argument-list
1296 // that begins with a type template-argument.
1297 struct __variant_visit_barrier_tag {
1298 _LIBCPP_HIDE_FROM_ABI explicit __variant_visit_barrier_tag() = default;
1299 };
1300
1301 template <__variant_visit_barrier_tag = __variant_visit_barrier_tag{}, class _Self, class _Visitor>
1302 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) visit(this _Self&& __self, _Visitor&& __visitor) {
1303 return std::visit(std::forward<_Visitor>(__visitor), std::__forward_as<_Self, variant>(__self));
1304 }
1305
1306 template <class _Rp, class _Self, class _Visitor>
1307 _LIBCPP_HIDE_FROM_ABI constexpr _Rp visit(this _Self&& __self, _Visitor&& __visitor) {
1308 return std::visit<_Rp>(std::forward<_Visitor>(__visitor), std::__forward_as<_Self, variant>(__self));
1309 }
1310# endif
1311
1312private:
1313 __variant_detail::__impl<_Types...> __impl_;
1314
1315 friend struct __variant_detail::__access::__variant;
1316 friend struct __variant_detail::__visitation::__variant;
1317};
1318
1319template <size_t _Ip, class... _Types>
1320_LIBCPP_HIDE_FROM_ABI constexpr bool __holds_alternative(const variant<_Types...>& __v) noexcept {
1321 return __v.index() == _Ip;
1322}
1323
1324template <class _Tp, class... _Types>
1325[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept {
1326 return std::__holds_alternative<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1327}
1328
1329template <size_t _Ip, class _Vp>
1330_LIBCPP_HIDE_FROM_ABI constexpr auto&& __generic_get(_Vp&& __v) {
1331 using __variant_detail::__access::__variant;
1332 if (!std::__holds_alternative<_Ip>(__v)) {
1333 std::__throw_bad_variant_access();
1334 }
1335 return __variant::__get_alt<_Ip>(std::forward<_Vp>(__v)).__value;
1336}
1337
1338template <size_t _Ip, class... _Types>
1339[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr variant_alternative_t<_Ip, variant<_Types...>>&
1340get(variant<_Types...>& __v) {
1341 static_assert(_Ip < sizeof...(_Types));
1342 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1343 return std::__generic_get<_Ip>(__v);
1344}
1345
1346template <size_t _Ip, class... _Types>
1347[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr variant_alternative_t<_Ip, variant<_Types...>>&&
1348get(variant<_Types...>&& __v) {
1349 static_assert(_Ip < sizeof...(_Types));
1350 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1351 return std::__generic_get<_Ip>(std::move(__v));
1352}
1353
1354template <size_t _Ip, class... _Types>
1355[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const variant_alternative_t<_Ip, variant<_Types...>>&
1356get(const variant<_Types...>& __v) {
1357 static_assert(_Ip < sizeof...(_Types));
1358 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1359 return std::__generic_get<_Ip>(__v);
1360}
1361
1362template <size_t _Ip, class... _Types>
1363[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const variant_alternative_t<_Ip, variant<_Types...>>&&
1364get(const variant<_Types...>&& __v) {
1365 static_assert(_Ip < sizeof...(_Types));
1366 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1367 return std::__generic_get<_Ip>(std::move(__v));
1368}
1369
1370template <class _Tp, class... _Types>
1371[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp& get(variant<_Types...>& __v) {
1372 static_assert(!is_void_v<_Tp>);
1373 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1374}
1375
1376template <class _Tp, class... _Types>
1377[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp&& get(variant<_Types...>&& __v) {
1378 static_assert(!is_void_v<_Tp>);
1379 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(std::move(__v));
1380}
1381
1382template <class _Tp, class... _Types>
1383[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const _Tp& get(const variant<_Types...>& __v) {
1384 static_assert(!is_void_v<_Tp>);
1385 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1386}
1387
1388template <class _Tp, class... _Types>
1389[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const _Tp&& get(const variant<_Types...>&& __v) {
1390 static_assert(!is_void_v<_Tp>);
1391 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(std::move(__v));
1392}
1393
1394template <size_t _Ip, class _Vp>
1395_LIBCPP_HIDE_FROM_ABI constexpr auto* __generic_get_if(_Vp* __v) noexcept {
1396 using __variant_detail::__access::__variant;
1397 return __v && std::__holds_alternative<_Ip>(*__v) ? std::addressof(__variant::__get_alt<_Ip>(*__v).__value) : nullptr;
1398}
1399
1400template <size_t _Ip, class... _Types>
1401[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<variant_alternative_t<_Ip, variant<_Types...>>>
1402get_if(variant<_Types...>* __v) noexcept {
1403 static_assert(_Ip < sizeof...(_Types));
1404 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1405 return std::__generic_get_if<_Ip>(__v);
1406}
1407
1408template <size_t _Ip, class... _Types>
1409[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<const variant_alternative_t<_Ip, variant<_Types...>>>
1410get_if(const variant<_Types...>* __v) noexcept {
1411 static_assert(_Ip < sizeof...(_Types));
1412 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1413 return std::__generic_get_if<_Ip>(__v);
1414}
1415
1416template <class _Tp, class... _Types>
1417[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<_Tp> get_if(variant<_Types...>* __v) noexcept {
1418 static_assert(!is_void_v<_Tp>);
1419 return std::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1420}
1421
1422template <class _Tp, class... _Types>
1423[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<const _Tp> get_if(const variant<_Types...>* __v) noexcept {
1424 static_assert(!is_void_v<_Tp>);
1425 return std::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1426}
1427
1428template <class _Operator>
1429struct __convert_to_bool {
1430 template <class _T1, class _T2>
1431 _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(_T1&& __t1, _T2&& __t2) const {
1432 static_assert(is_convertible<decltype(_Operator{}(std::forward<_T1>(__t1), std::forward<_T2>(__t2))), bool>::value,
1433 "the relational operator does not return a type which is implicitly convertible to bool");
1434 return _Operator{}(std::forward<_T1>(__t1), std::forward<_T2>(__t2));
1435 }
1436};
1437
1438template <class... _Types>
1439# if _LIBCPP_STD_VER >= 26
1440 requires(requires(const _Types& __t) {
1441 { __t == __t } -> __core_convertible_to<bool>;
1442 } && ...)
1443# endif
1444_LIBCPP_HIDE_FROM_ABI constexpr bool operator==(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1445 using __variant_detail::__visitation::__variant;
1446 if (__lhs.index() != __rhs.index())
1447 return false;
1448 if (__lhs.valueless_by_exception())
1449 return true;
1450 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<equal_to<>>{}, __lhs, __rhs);
1451}
1452
1453# if _LIBCPP_STD_VER >= 20
1454
1455template <class... _Types>
1456 requires(three_way_comparable<_Types> && ...)
1457_LIBCPP_HIDE_FROM_ABI constexpr common_comparison_category_t<compare_three_way_result_t<_Types>...>
1458operator<=>(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1459 using __variant_detail::__visitation::__variant;
1460 using __result_t = common_comparison_category_t<compare_three_way_result_t<_Types>...>;
1461 if (__lhs.valueless_by_exception() && __rhs.valueless_by_exception())
1462 return strong_ordering::equal;
1463 if (__lhs.valueless_by_exception())
1464 return strong_ordering::less;
1465 if (__rhs.valueless_by_exception())
1466 return strong_ordering::greater;
1467 if (auto __c = __lhs.index() <=> __rhs.index(); __c != 0)
1468 return __c;
1469 auto __three_way = []<class _Type>(const _Type& __v, const _Type& __w) -> __result_t { return __v <=> __w; };
1470 return __variant::__visit_value_at(__lhs.index(), __three_way, __lhs, __rhs);
1471}
1472
1473# endif // _LIBCPP_STD_VER >= 20
1474
1475template <class... _Types>
1476# if _LIBCPP_STD_VER >= 26
1477 requires(requires(const _Types& __t) {
1478 { __t != __t } -> __core_convertible_to<bool>;
1479 } && ...)
1480# endif
1481_LIBCPP_HIDE_FROM_ABI constexpr bool operator!=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1482 using __variant_detail::__visitation::__variant;
1483 if (__lhs.index() != __rhs.index())
1484 return true;
1485 if (__lhs.valueless_by_exception())
1486 return false;
1487 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<not_equal_to<>>{}, __lhs, __rhs);
1488}
1489
1490template <class... _Types>
1491# if _LIBCPP_STD_VER >= 26
1492 requires(requires(const _Types& __t) {
1493 { __t < __t } -> __core_convertible_to<bool>;
1494 } && ...)
1495# endif
1496_LIBCPP_HIDE_FROM_ABI constexpr bool operator<(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1497 using __variant_detail::__visitation::__variant;
1498 if (__rhs.valueless_by_exception())
1499 return false;
1500 if (__lhs.valueless_by_exception())
1501 return true;
1502 if (__lhs.index() < __rhs.index())
1503 return true;
1504 if (__lhs.index() > __rhs.index())
1505 return false;
1506 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<less<>>{}, __lhs, __rhs);
1507}
1508
1509template <class... _Types>
1510# if _LIBCPP_STD_VER >= 26
1511 requires(requires(const _Types& __t) {
1512 { __t > __t } -> __core_convertible_to<bool>;
1513 } && ...)
1514# endif
1515_LIBCPP_HIDE_FROM_ABI constexpr bool operator>(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1516 using __variant_detail::__visitation::__variant;
1517 if (__lhs.valueless_by_exception())
1518 return false;
1519 if (__rhs.valueless_by_exception())
1520 return true;
1521 if (__lhs.index() > __rhs.index())
1522 return true;
1523 if (__lhs.index() < __rhs.index())
1524 return false;
1525 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<greater<>>{}, __lhs, __rhs);
1526}
1527
1528template <class... _Types>
1529# if _LIBCPP_STD_VER >= 26
1530 requires(requires(const _Types& __t) {
1531 { __t <= __t } -> __core_convertible_to<bool>;
1532 } && ...)
1533# endif
1534_LIBCPP_HIDE_FROM_ABI constexpr bool operator<=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1535 using __variant_detail::__visitation::__variant;
1536 if (__lhs.valueless_by_exception())
1537 return true;
1538 if (__rhs.valueless_by_exception())
1539 return false;
1540 if (__lhs.index() < __rhs.index())
1541 return true;
1542 if (__lhs.index() > __rhs.index())
1543 return false;
1544 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<less_equal<>>{}, __lhs, __rhs);
1545}
1546
1547template <class... _Types>
1548# if _LIBCPP_STD_VER >= 26
1549 requires(requires(const _Types& __t) {
1550 { __t >= __t } -> __core_convertible_to<bool>;
1551 } && ...)
1552# endif
1553_LIBCPP_HIDE_FROM_ABI constexpr bool operator>=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1554 using __variant_detail::__visitation::__variant;
1555 if (__rhs.valueless_by_exception())
1556 return true;
1557 if (__lhs.valueless_by_exception())
1558 return false;
1559 if (__lhs.index() > __rhs.index())
1560 return true;
1561 if (__lhs.index() < __rhs.index())
1562 return false;
1563 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<greater_equal<>>{}, __lhs, __rhs);
1564}
1565
1566template <class... _Vs>
1567_LIBCPP_HIDE_FROM_ABI constexpr void __throw_if_valueless(_Vs&&... __vs) {
1568 const bool __valueless = (... || std::__as_variant(__vs).valueless_by_exception());
1569 if (__valueless) {
1570 std::__throw_bad_variant_access();
1571 }
1572}
1573
1574template < class _Visitor, class... _Vs, typename>
1575_LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
1576 using __variant_detail::__visitation::__variant;
1577 std::__throw_if_valueless(std::forward<_Vs>(__vs)...);
1578 return __variant::__visit_value(std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs)...);
1579}
1580
1581# if _LIBCPP_STD_VER >= 20
1582template < class _Rp, class _Visitor, class... _Vs, typename>
1583_LIBCPP_HIDE_FROM_ABI constexpr _Rp visit(_Visitor&& __visitor, _Vs&&... __vs) {
1584 using __variant_detail::__visitation::__variant;
1585 std::__throw_if_valueless(std::forward<_Vs>(__vs)...);
1586 return __variant::__visit_value<_Rp>(std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs)...);
1587}
1588# endif
1589
1590template <class... _Types>
1591_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 auto
1592swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs)))
1593 -> decltype(__lhs.swap(__rhs)) {
1594 return __lhs.swap(__rhs);
1595}
1596
1597template <class... _Types>
1598struct hash< __enable_hash_helper<variant<_Types...>, remove_const_t<_Types>...>> {
1599# if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
1600 using argument_type _LIBCPP_DEPRECATED_IN_CXX17 = variant<_Types...>;
1601 using result_type _LIBCPP_DEPRECATED_IN_CXX17 = size_t;
1602# endif
1603
1604 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI size_t operator()(const variant<_Types...>& __v) const {
1605 using __variant_detail::__visitation::__variant;
1606 size_t __res =
1607 __v.valueless_by_exception()
1608 ? 299792458 // Random value chosen by the universe upon creation
1609 : __variant::__visit_alt(
1610 [](const auto& __alt) {
1611 using __alt_type = __remove_cvref_t<decltype(__alt)>;
1612 using __value_type = remove_const_t< typename __alt_type::__value_type>;
1613 return hash<__value_type>{}(__alt.__value);
1614 },
1615 __v);
1616 return std::__hash_combine(lhs: __res, rhs: hash<size_t>{}(__v.index()));
1617 }
1618};
1619
1620// __unchecked_get is the same as std::get, except, it is UB to use it with the wrong
1621// type whereas std::get will throw or returning nullptr. This makes it faster than
1622// std::get.
1623template <size_t _Ip, class _Vp>
1624_LIBCPP_HIDE_FROM_ABI constexpr auto&& __unchecked_get(_Vp&& __v) noexcept {
1625 using __variant_detail::__access::__variant;
1626 return __variant::__get_alt<_Ip>(std::forward<_Vp>(__v)).__value;
1627}
1628
1629template <class _Tp, class... _Types>
1630_LIBCPP_HIDE_FROM_ABI constexpr auto&& __unchecked_get(const variant<_Types...>& __v) noexcept {
1631 return std::__unchecked_get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1632}
1633
1634template <class _Tp, class... _Types>
1635_LIBCPP_HIDE_FROM_ABI constexpr auto&& __unchecked_get(variant<_Types...>& __v) noexcept {
1636 return std::__unchecked_get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1637}
1638
1639# endif // _LIBCPP_STD_VER >= 17
1640
1641_LIBCPP_END_NAMESPACE_STD
1642
1643_LIBCPP_POP_MACROS
1644
1645# if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
1646# include <cstddef>
1647# include <exception>
1648# include <tuple>
1649# include <type_traits>
1650# include <typeinfo>
1651# include <utility>
1652# endif
1653#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
1654
1655#endif // _LIBCPP_VARIANT
1656