master
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_replaceable.h>
251# include <__type_traits/is_same.h>
252# include <__type_traits/is_swappable.h>
253# include <__type_traits/is_trivially_assignable.h>
254# include <__type_traits/is_trivially_constructible.h>
255# include <__type_traits/is_trivially_destructible.h>
256# include <__type_traits/is_trivially_relocatable.h>
257# include <__type_traits/is_void.h>
258# include <__type_traits/remove_const.h>
259# include <__type_traits/remove_cvref.h>
260# include <__type_traits/remove_reference.h>
261# include <__type_traits/type_identity.h>
262# include <__type_traits/void_t.h>
263# include <__utility/declval.h>
264# include <__utility/forward.h>
265# include <__utility/forward_like.h>
266# include <__utility/in_place.h>
267# include <__utility/integer_sequence.h>
268# include <__utility/move.h>
269# include <__utility/swap.h>
270# include <__variant/monostate.h>
271# include <__verbose_abort>
272# include <initializer_list>
273# include <limits>
274# include <version>
275
276// standard-mandated includes
277
278// [variant.syn]
279# include <compare>
280
281# if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
282# pragma GCC system_header
283# endif
284
285_LIBCPP_PUSH_MACROS
286# include <__undef_macros>
287
288_LIBCPP_BEGIN_UNVERSIONED_NAMESPACE_STD
289
290class _LIBCPP_EXPORTED_FROM_ABI bad_variant_access : public exception {
291public:
292 const char* what() const _NOEXCEPT override;
293};
294
295_LIBCPP_END_UNVERSIONED_NAMESPACE_STD
296
297_LIBCPP_BEGIN_NAMESPACE_STD
298
299# if _LIBCPP_STD_VER >= 17
300
301// Light N-dimensional array of function pointers. Used in place of std::array to avoid
302// adding a dependency.
303template <class _Tp, size_t _Size>
304struct __farray {
305 static_assert(_Size > 0, "N-dimensional array should never be empty in std::visit");
306 _Tp __buf_[_Size] = {};
307
308 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp& operator[](size_t __n) const noexcept { return __buf_[__n]; }
309};
310
311[[noreturn]] inline _LIBCPP_HIDE_FROM_ABI void __throw_bad_variant_access() {
312# if _LIBCPP_HAS_EXCEPTIONS
313 throw bad_variant_access();
314# else
315 _LIBCPP_VERBOSE_ABORT("bad_variant_access was thrown in -fno-exceptions mode");
316# endif
317}
318
319// variant_size
320template <class _Tp>
321struct variant_size<const _Tp> : variant_size<_Tp> {};
322
323template <class _Tp>
324struct variant_size<volatile _Tp> : variant_size<_Tp> {};
325
326template <class _Tp>
327struct variant_size<const volatile _Tp> : variant_size<_Tp> {};
328
329template <class... _Types>
330struct variant_size<variant<_Types...>> : integral_constant<size_t, sizeof...(_Types)> {};
331
332// variant_alternative
333template <size_t _Ip, class _Tp>
334struct variant_alternative<_Ip, const _Tp> : add_const<variant_alternative_t<_Ip, _Tp>> {};
335
336template <size_t _Ip, class _Tp>
337struct variant_alternative<_Ip, volatile _Tp> : add_volatile<variant_alternative_t<_Ip, _Tp>> {};
338
339template <size_t _Ip, class _Tp>
340struct variant_alternative<_Ip, const volatile _Tp> : add_cv<variant_alternative_t<_Ip, _Tp>> {};
341
342template <size_t _Ip, class... _Types>
343struct variant_alternative<_Ip, variant<_Types...>> {
344 static_assert(_Ip < sizeof...(_Types), "Index out of bounds in std::variant_alternative<>");
345 using type _LIBCPP_NODEBUG = __type_pack_element<_Ip, _Types...>;
346};
347
348template <size_t _NumAlternatives>
349_LIBCPP_HIDE_FROM_ABI constexpr auto __choose_index_type() {
350# ifdef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
351 if constexpr (_NumAlternatives < numeric_limits<unsigned char>::max())
352 return static_cast<unsigned char>(0);
353 else if constexpr (_NumAlternatives < numeric_limits<unsigned short>::max())
354 return static_cast<unsigned short>(0);
355 else
356# endif // _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
357 return static_cast<unsigned int>(0);
358}
359
360template <size_t _NumAlts>
361using __variant_index_t _LIBCPP_NODEBUG = decltype(std::__choose_index_type<_NumAlts>());
362
363template <class _IndexType>
364constexpr _IndexType __variant_npos = static_cast<_IndexType>(-1);
365
366template <class... _Types>
367_LIBCPP_HIDE_FROM_ABI constexpr variant<_Types...>& __as_variant(variant<_Types...>& __vs) noexcept {
368 return __vs;
369}
370
371template <class... _Types>
372_LIBCPP_HIDE_FROM_ABI constexpr const variant<_Types...>& __as_variant(const variant<_Types...>& __vs) noexcept {
373 return __vs;
374}
375
376template <class... _Types>
377_LIBCPP_HIDE_FROM_ABI constexpr variant<_Types...>&& __as_variant(variant<_Types...>&& __vs) noexcept {
378 return std::move(__vs);
379}
380
381template <class... _Types>
382_LIBCPP_HIDE_FROM_ABI constexpr const variant<_Types...>&& __as_variant(const variant<_Types...>&& __vs) noexcept {
383 return std::move(__vs);
384}
385
386namespace __find_detail {
387
388template <class _Tp, class... _Types>
389_LIBCPP_HIDE_FROM_ABI constexpr size_t __find_index() {
390 constexpr bool __matches[] = {is_same_v<_Tp, _Types>...};
391 size_t __result = __not_found;
392 for (size_t __i = 0; __i < sizeof...(_Types); ++__i) {
393 if (__matches[__i]) {
394 if (__result != __not_found) {
395 return __ambiguous;
396 }
397 __result = __i;
398 }
399 }
400 return __result;
401}
402
403template <size_t _Index>
404struct __find_unambiguous_index_sfinae_impl : integral_constant<size_t, _Index> {};
405
406template <>
407struct __find_unambiguous_index_sfinae_impl<__not_found> {};
408
409template <>
410struct __find_unambiguous_index_sfinae_impl<__ambiguous> {};
411
412template <class _Tp, class... _Types>
413struct __find_unambiguous_index_sfinae
414 : __find_unambiguous_index_sfinae_impl<__find_detail::__find_index<_Tp, _Types...>()> {};
415
416} // namespace __find_detail
417
418namespace __variant_detail {
419
420struct __valueless_t {};
421
422enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
423
424template <typename _Tp, template <typename> class _IsTriviallyAvailable, template <typename> class _IsAvailable>
425constexpr _Trait __trait =
426 _IsTriviallyAvailable<_Tp>::value ? _Trait::_TriviallyAvailable
427 : _IsAvailable<_Tp>::value
428 ? _Trait::_Available
429 : _Trait::_Unavailable;
430
431_LIBCPP_HIDE_FROM_ABI constexpr _Trait __common_trait(initializer_list<_Trait> __traits) {
432 _Trait __result = _Trait::_TriviallyAvailable;
433 for (_Trait __t : __traits) {
434 if (static_cast<int>(__t) > static_cast<int>(__result)) {
435 __result = __t;
436 }
437 }
438 return __result;
439}
440
441template <typename... _Types>
442struct __traits {
443 static constexpr _Trait __copy_constructible_trait =
444 __variant_detail::__common_trait({__trait<_Types, is_trivially_copy_constructible, is_copy_constructible>...});
445
446 static constexpr _Trait __move_constructible_trait =
447 __variant_detail::__common_trait({__trait<_Types, is_trivially_move_constructible, is_move_constructible>...});
448
449 static constexpr _Trait __copy_assignable_trait = __variant_detail::__common_trait(
450 {__copy_constructible_trait, __trait<_Types, is_trivially_copy_assignable, is_copy_assignable>...});
451
452 static constexpr _Trait __move_assignable_trait = __variant_detail::__common_trait(
453 {__move_constructible_trait, __trait<_Types, is_trivially_move_assignable, is_move_assignable>...});
454
455 static constexpr _Trait __destructible_trait =
456 __variant_detail::__common_trait({__trait<_Types, is_trivially_destructible, is_destructible>...});
457};
458
459namespace __access {
460
461struct __union {
462 template <class _Vp>
463 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<0>) {
464 return std::forward<_Vp>(__v).__head;
465 }
466
467 template <class _Vp, size_t _Ip>
468 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<_Ip>) {
469 return __get_alt(std::forward<_Vp>(__v).__tail, in_place_index<_Ip - 1>);
470 }
471};
472
473struct __base {
474 template <size_t _Ip, class _Vp>
475 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v) {
476 return __union::__get_alt(std::forward<_Vp>(__v).__data, in_place_index<_Ip>);
477 }
478};
479
480struct __variant {
481 template <size_t _Ip, class _Vp>
482 _LIBCPP_HIDE_FROM_ABI static constexpr auto&& __get_alt(_Vp&& __v) {
483 return __base::__get_alt<_Ip>(std::forward<_Vp>(__v).__impl_);
484 }
485};
486
487} // namespace __access
488
489namespace __visitation {
490
491struct __base {
492 template <class _Visitor, class... _Vs>
493 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto)
494 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
495 constexpr auto __fdiagonal = __make_fdiagonal<_Visitor&&, decltype(std::forward<_Vs>(__vs).__as_base())...>();
496 return __fdiagonal[__index](std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs).__as_base()...);
497 }
498
499 template <class _Visitor, class... _Vs>
500 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor, _Vs&&... __vs) {
501 constexpr auto __fmatrix = __make_fmatrix<_Visitor&&, decltype(std::forward<_Vs>(__vs).__as_base())...>();
502 return __at(__fmatrix, __vs.index()...)(std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs).__as_base()...);
503 }
504
505private:
506 template <class _Tp>
507 _LIBCPP_HIDE_FROM_ABI static constexpr const _Tp& __at(const _Tp& __elem) {
508 return __elem;
509 }
510
511 template <class _Tp, size_t _Np, typename... _Indices>
512 _LIBCPP_HIDE_FROM_ABI static constexpr auto&&
513 __at(const __farray<_Tp, _Np>& __elems, size_t __index, _Indices... __indices) {
514 return __at(__elems[__index], __indices...);
515 }
516
517 template <class _Fp, class... _Fs>
518 static _LIBCPP_HIDE_FROM_ABI constexpr void __std_visit_visitor_return_type_check() {
519 static_assert(
520 __all<is_same_v<_Fp, _Fs>...>::value, "`std::visit` requires the visitor to have a single return type.");
521 }
522
523 template <class... _Fs>
524 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_farray(_Fs&&... __fs) {
525 __std_visit_visitor_return_type_check<__remove_cvref_t<_Fs>...>();
526 using __result = __farray<common_type_t<__remove_cvref_t<_Fs>...>, sizeof...(_Fs)>;
527 return __result{{std::forward<_Fs>(__fs)...}};
528 }
529
530 template <size_t... _Is>
531 struct __dispatcher {
532 template <class _Fp, class... _Vs>
533 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
534 return std::__invoke(static_cast<_Fp>(__f), __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
535 }
536 };
537
538 template <class _Fp, class... _Vs, size_t... _Is>
539 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_dispatch(index_sequence<_Is...>) {
540 return __dispatcher<_Is...>::template __dispatch<_Fp, _Vs...>;
541 }
542
543 template <size_t _Ip, class _Fp, class... _Vs>
544 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fdiagonal_impl() {
545 return __make_dispatch<_Fp, _Vs...>(index_sequence<((void)__type_identity<_Vs>{}, _Ip)...>{});
546 }
547
548 template <class _Fp, class... _Vs, size_t... _Is>
549 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
550 return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
551 }
552
553 template <class _Fp, class _Vp, class... _Vs>
554 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fdiagonal() {
555 constexpr size_t __np = __remove_cvref_t<_Vp>::__size();
556 static_assert(__all<(__np == __remove_cvref_t<_Vs>::__size())...>::value);
557 return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<__np>{});
558 }
559
560 template <class _Fp, class... _Vs, size_t... _Is>
561 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
562 return __make_dispatch<_Fp, _Vs...>(__is);
563 }
564
565 template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
566 _LIBCPP_HIDE_FROM_ABI static constexpr auto
567 __make_fmatrix_impl(index_sequence<_Is...>, index_sequence<_Js...>, _Ls... __ls) {
568 return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(index_sequence<_Is..., _Js>{}, __ls...)...);
569 }
570
571 template <class _Fp, class... _Vs>
572 _LIBCPP_HIDE_FROM_ABI static constexpr auto __make_fmatrix() {
573 return __make_fmatrix_impl<_Fp, _Vs...>(
574 index_sequence<>{}, make_index_sequence<__remove_cvref_t<_Vs>::__size()>{}...);
575 }
576};
577
578struct __variant {
579 template <class _Visitor, class... _Vs>
580 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto)
581 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
582 return __base::__visit_alt_at(__index, std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs).__impl_...);
583 }
584
585 template <class _Visitor, class... _Vs>
586 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor, _Vs&&... __vs) {
587 return __base::__visit_alt(
588 std::forward<_Visitor>(__visitor), std::__as_variant(std::forward<_Vs>(__vs)).__impl_...);
589 }
590
591 template <class _Visitor, class... _Vs>
592 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto)
593 __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
594 return __visit_alt_at(__index, __make_value_visitor(std::forward<_Visitor>(__visitor)), std::forward<_Vs>(__vs)...);
595 }
596
597 template <class _Visitor, class... _Vs>
598 _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __visit_value(_Visitor&& __visitor, _Vs&&... __vs) {
599 return __visit_alt(__make_value_visitor(std::forward<_Visitor>(__visitor)), std::forward<_Vs>(__vs)...);
600 }
601
602# if _LIBCPP_STD_VER >= 20
603 template <class _Rp, class _Visitor, class... _Vs>
604 _LIBCPP_HIDE_FROM_ABI static constexpr _Rp __visit_value(_Visitor&& __visitor, _Vs&&... __vs) {
605 return __visit_alt(__make_value_visitor<_Rp>(std::forward<_Visitor>(__visitor)), std::forward<_Vs>(__vs)...);
606 }
607# endif
608
609private:
610 template <class _Visitor, class... _Values>
611 static _LIBCPP_HIDE_FROM_ABI constexpr void __std_visit_exhaustive_visitor_check() {
612 static_assert(is_invocable_v<_Visitor, _Values...>, "`std::visit` requires the visitor to be exhaustive.");
613 }
614
615 template <class _Visitor>
616 struct __value_visitor {
617 template <class... _Alts>
618 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator()(_Alts&&... __alts) const {
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 {
922 struct {
923 _LIBCPP_HIDDEN _LIBCPP_CONSTEXPR_SINCE_CXX20 void operator()(true_type) const {
924 __this->__emplace<_Ip>(std::forward<_Arg>(__arg));
925 }
926 _LIBCPP_HIDDEN _LIBCPP_CONSTEXPR_SINCE_CXX20 void operator()(false_type) const {
927 __this->__emplace<_Ip>(_Tp(std::forward<_Arg>(__arg)));
928 }
929 __assignment* __this;
930 _Arg&& __arg;
931 } __impl{this, std::forward<_Arg>(__arg)};
932 __impl(bool_constant < is_nothrow_constructible_v<_Tp, _Arg> || !is_nothrow_move_constructible_v < _Tp >> {});
933 }
934 }
935
936 template <class _That>
937 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __generic_assign(_That&& __that) {
938 if (this->valueless_by_exception() && __that.valueless_by_exception()) {
939 // do nothing.
940 } else if (__that.valueless_by_exception()) {
941 this->__destroy();
942 } else {
943 __visitation::__base::__visit_alt_at(
944 __that.index(),
945 [this](auto& __this_alt, auto&& __that_alt) {
946 this->__assign_alt(__this_alt, std::forward<decltype(__that_alt)>(__that_alt).__value);
947 },
948 *this,
949 std::forward<_That>(__that));
950 }
951 }
952};
953
954template <class _Traits, _Trait = _Traits::__move_assignable_trait>
955class __move_assignment;
956
957# define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, move_assignment_definition) \
958 template <class... _Types> \
959 class __move_assignment<__traits<_Types...>, move_assignable_trait> : public __assignment<__traits<_Types...>> { \
960 using __base_type _LIBCPP_NODEBUG = __assignment<__traits<_Types...>>; \
961 \
962 public: \
963 using __base_type::__base_type; \
964 using __base_type::operator=; \
965 \
966 _LIBCPP_HIDE_FROM_ABI __move_assignment(const __move_assignment&) = default; \
967 _LIBCPP_HIDE_FROM_ABI __move_assignment(__move_assignment&&) = default; \
968 _LIBCPP_HIDE_FROM_ABI ~__move_assignment() = default; \
969 _LIBCPP_HIDE_FROM_ABI __move_assignment& operator=(const __move_assignment&) = default; \
970 move_assignment_definition; \
971 }
972
973_LIBCPP_VARIANT_MOVE_ASSIGNMENT(_Trait::_TriviallyAvailable,
974 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_assignment& operator=(
975 __move_assignment&& __that) = default);
976
977_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
978 _Trait::_Available,
979 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_assignment&
980 operator=(__move_assignment&& __that) noexcept(
981 __all<(is_nothrow_move_constructible_v<_Types> && is_nothrow_move_assignable_v<_Types>)...>::value) {
982 this->__generic_assign(std::move(__that));
983 return *this;
984 } _LIBCPP_EAT_SEMICOLON);
985
986_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
987 _Trait::_Unavailable,
988 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __move_assignment& operator=(__move_assignment&&) = delete);
989
990# undef _LIBCPP_VARIANT_MOVE_ASSIGNMENT
991
992template <class _Traits, _Trait = _Traits::__copy_assignable_trait>
993class __copy_assignment;
994
995# define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, copy_assignment_definition) \
996 template <class... _Types> \
997 class __copy_assignment<__traits<_Types...>, copy_assignable_trait> \
998 : public __move_assignment<__traits<_Types...>> { \
999 using __base_type _LIBCPP_NODEBUG = __move_assignment<__traits<_Types...>>; \
1000 \
1001 public: \
1002 using __base_type::__base_type; \
1003 using __base_type::operator=; \
1004 \
1005 _LIBCPP_HIDE_FROM_ABI __copy_assignment(const __copy_assignment&) = default; \
1006 _LIBCPP_HIDE_FROM_ABI __copy_assignment(__copy_assignment&&) = default; \
1007 _LIBCPP_HIDE_FROM_ABI ~__copy_assignment() = default; \
1008 _LIBCPP_HIDE_FROM_ABI __copy_assignment& operator=(__copy_assignment&&) = default; \
1009 copy_assignment_definition; \
1010 }
1011
1012_LIBCPP_VARIANT_COPY_ASSIGNMENT(_Trait::_TriviallyAvailable,
1013 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_assignment& operator=(
1014 const __copy_assignment& __that) = default);
1015
1016_LIBCPP_VARIANT_COPY_ASSIGNMENT(
1017 _Trait::_Available,
1018 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_assignment&
1019 operator=(const __copy_assignment& __that) {
1020 this->__generic_assign(__that);
1021 return *this;
1022 } _LIBCPP_EAT_SEMICOLON);
1023
1024_LIBCPP_VARIANT_COPY_ASSIGNMENT(_Trait::_Unavailable,
1025 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __copy_assignment& operator=(
1026 const __copy_assignment&) = delete);
1027
1028# undef _LIBCPP_VARIANT_COPY_ASSIGNMENT
1029
1030template <class... _Types>
1031class __impl : public __copy_assignment<__traits<_Types...>> {
1032 using __base_type _LIBCPP_NODEBUG = __copy_assignment<__traits<_Types...>>;
1033
1034public:
1035 using __base_type::__base_type; // get in_place_index_t constructor & friends
1036 _LIBCPP_HIDE_FROM_ABI __impl(__impl const&) = default;
1037 _LIBCPP_HIDE_FROM_ABI __impl(__impl&&) = default;
1038 _LIBCPP_HIDE_FROM_ABI __impl& operator=(__impl const&) = default;
1039 _LIBCPP_HIDE_FROM_ABI __impl& operator=(__impl&&) = default;
1040
1041 template <size_t _Ip, class _Arg>
1042 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __assign(_Arg&& __arg) {
1043 this->__assign_alt(__access::__base::__get_alt<_Ip>(*this), std::forward<_Arg>(__arg));
1044 }
1045
1046 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __swap(__impl& __that) {
1047 if (this->valueless_by_exception() && __that.valueless_by_exception()) {
1048 // do nothing.
1049 } else if (this->index() == __that.index()) {
1050 __visitation::__base::__visit_alt_at(
1051 this->index(),
1052 [](auto& __this_alt, auto& __that_alt) {
1053 using std::swap;
1054 swap(__this_alt.__value, __that_alt.__value);
1055 },
1056 *this,
1057 __that);
1058 } else {
1059 __impl* __lhs = this;
1060 __impl* __rhs = std::addressof(__that);
1061 if (__lhs->__move_nothrow() && !__rhs->__move_nothrow()) {
1062 std::swap(__lhs, __rhs);
1063 }
1064 __impl __tmp(std::move(*__rhs));
1065# if _LIBCPP_HAS_EXCEPTIONS
1066 if constexpr (__all<is_nothrow_move_constructible_v<_Types>...>::value) {
1067 this->__generic_construct(*__rhs, std::move(*__lhs));
1068 } else {
1069 // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
1070 // and `__tmp` is nothrow move constructible then we move `__tmp` back
1071 // into `__rhs` and provide the strong exception safety guarantee.
1072 try {
1073 this->__generic_construct(*__rhs, std::move(*__lhs));
1074 } catch (...) {
1075 if (__tmp.__move_nothrow()) {
1076 this->__generic_construct(*__rhs, std::move(__tmp));
1077 }
1078 throw;
1079 }
1080 }
1081# else
1082 // this isn't consolidated with the `if constexpr` branch above due to
1083 // `throw` being ill-formed with exceptions disabled even when discarded.
1084 this->__generic_construct(*__rhs, std::move(*__lhs));
1085# endif
1086 this->__generic_construct(*__lhs, std::move(__tmp));
1087 }
1088 }
1089
1090private:
1091 constexpr inline _LIBCPP_HIDE_FROM_ABI bool __move_nothrow() const {
1092 constexpr bool __results[] = {is_nothrow_move_constructible_v<_Types>...};
1093 return this->valueless_by_exception() || __results[this->index()];
1094 }
1095};
1096
1097struct __no_narrowing_check {
1098 template <class _Dest, class _Source>
1099 using _Apply _LIBCPP_NODEBUG = __type_identity<_Dest>;
1100};
1101
1102struct __narrowing_check {
1103 template <class _Dest>
1104 static auto __test_impl(_Dest (&&)[1]) -> __type_identity<_Dest>;
1105 template <class _Dest, class _Source>
1106 using _Apply _LIBCPP_NODEBUG = decltype(__test_impl<_Dest>({std::declval<_Source>()}));
1107};
1108
1109template <class _Dest, class _Source>
1110using __check_for_narrowing _LIBCPP_NODEBUG =
1111 typename _If< is_arithmetic<_Dest>::value, __narrowing_check, __no_narrowing_check >::template _Apply<_Dest,
1112 _Source>;
1113
1114template <class _Tp, size_t _Idx>
1115struct __overload {
1116 template <class _Up>
1117 auto operator()(_Tp, _Up&&) const -> __check_for_narrowing<_Tp, _Up>;
1118};
1119
1120template <class... _Bases>
1121struct __all_overloads : _Bases... {
1122 void operator()() const;
1123 using _Bases::operator()...;
1124};
1125
1126template <class _IdxSeq>
1127struct __make_overloads_imp;
1128
1129template <size_t... _Idx>
1130struct __make_overloads_imp<__tuple_indices<_Idx...> > {
1131 template <class... _Types>
1132 using _Apply _LIBCPP_NODEBUG = __all_overloads<__overload<_Types, _Idx>...>;
1133};
1134
1135template <class... _Types>
1136using _MakeOverloads _LIBCPP_NODEBUG =
1137 typename __make_overloads_imp< __make_indices_imp<sizeof...(_Types), 0> >::template _Apply<_Types...>;
1138
1139template <class _Tp, class... _Types>
1140using __best_match_t _LIBCPP_NODEBUG = typename invoke_result_t<_MakeOverloads<_Types...>, _Tp, _Tp>::type;
1141
1142} // namespace __variant_detail
1143
1144template <class _Visitor, class... _Vs, typename = void_t<decltype(std::__as_variant(std::declval<_Vs>()))...>>
1145_LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs);
1146
1147# if _LIBCPP_STD_VER >= 20
1148template <class _Rp,
1149 class _Visitor,
1150 class... _Vs,
1151 typename = void_t<decltype(std::__as_variant(std::declval<_Vs>()))...>>
1152_LIBCPP_HIDE_FROM_ABI constexpr _Rp visit(_Visitor&& __visitor, _Vs&&... __vs);
1153# endif
1154
1155template <class... _Types>
1156class _LIBCPP_DECLSPEC_EMPTY_BASES _LIBCPP_NO_SPECIALIZATIONS variant
1157 : private __sfinae_ctor_base< __all<is_copy_constructible_v<_Types>...>::value,
1158 __all<is_move_constructible_v<_Types>...>::value>,
1159 private __sfinae_assign_base<
1160 __all<(is_copy_constructible_v<_Types> && is_copy_assignable_v<_Types>)...>::value,
1161 __all<(is_move_constructible_v<_Types> && is_move_assignable_v<_Types>)...>::value> {
1162 static_assert(0 < sizeof...(_Types), "variant must consist of at least one alternative.");
1163
1164 static_assert(__all<!is_array_v<_Types>...>::value, "variant can not have an array type as an alternative.");
1165
1166 static_assert(__all<!is_reference_v<_Types>...>::value, "variant can not have a reference type as an alternative.");
1167
1168 static_assert(__all<!is_void_v<_Types>...>::value, "variant can not have a void type as an alternative.");
1169
1170 using __first_type _LIBCPP_NODEBUG = variant_alternative_t<0, variant>;
1171
1172public:
1173 using __trivially_relocatable _LIBCPP_NODEBUG =
1174 conditional_t<_And<__libcpp_is_trivially_relocatable<_Types>...>::value, variant, void>;
1175 using __replaceable _LIBCPP_NODEBUG = conditional_t<_And<__is_replaceable<_Types>...>::value, variant, void>;
1176
1177 template <bool _Dummy = true,
1178 enable_if_t<__dependent_type<is_default_constructible<__first_type>, _Dummy>::value, int> = 0>
1179 _LIBCPP_HIDE_FROM_ABI constexpr variant() noexcept(is_nothrow_default_constructible_v<__first_type>)
1180 : __impl_(in_place_index<0>) {}
1181
1182 _LIBCPP_HIDE_FROM_ABI constexpr variant(const variant&) = default;
1183 _LIBCPP_HIDE_FROM_ABI constexpr variant(variant&&) = default;
1184
1185 template < class _Arg,
1186 enable_if_t<!is_same_v<__remove_cvref_t<_Arg>, variant>, int> = 0,
1187 enable_if_t<!__is_inplace_type<__remove_cvref_t<_Arg>>::value, int> = 0,
1188 enable_if_t<!__is_inplace_index<__remove_cvref_t<_Arg>>::value, int> = 0,
1189 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1190 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1191 enable_if_t<is_constructible_v<_Tp, _Arg>, int> = 0>
1192 _LIBCPP_HIDE_FROM_ABI constexpr variant(_Arg&& __arg) noexcept(is_nothrow_constructible_v<_Tp, _Arg>)
1193 : __impl_(in_place_index<_Ip>, std::forward<_Arg>(__arg)) {}
1194
1195 template <size_t _Ip,
1196 class... _Args,
1197 class = enable_if_t<(_Ip < sizeof...(_Types)), int>,
1198 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1199 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1200 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(in_place_index_t<_Ip>, _Args&&... __args) noexcept(
1201 is_nothrow_constructible_v<_Tp, _Args...>)
1202 : __impl_(in_place_index<_Ip>, std::forward<_Args>(__args)...) {}
1203
1204 template < size_t _Ip,
1205 class _Up,
1206 class... _Args,
1207 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1208 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1209 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1210 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(
1211 in_place_index_t<_Ip>,
1212 initializer_list<_Up> __il,
1213 _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
1214 : __impl_(in_place_index<_Ip>, __il, std::forward<_Args>(__args)...) {}
1215
1216 template < class _Tp,
1217 class... _Args,
1218 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1219 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1220 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(in_place_type_t<_Tp>, _Args&&... __args) noexcept(
1221 is_nothrow_constructible_v<_Tp, _Args...>)
1222 : __impl_(in_place_index<_Ip>, std::forward<_Args>(__args)...) {}
1223
1224 template < class _Tp,
1225 class _Up,
1226 class... _Args,
1227 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1228 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1229 _LIBCPP_HIDE_FROM_ABI explicit constexpr variant(
1230 in_place_type_t<_Tp>,
1231 initializer_list<_Up> __il,
1232 _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, initializer_list< _Up>&, _Args...>)
1233 : __impl_(in_place_index<_Ip>, __il, std::forward<_Args>(__args)...) {}
1234
1235 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~variant() = default;
1236
1237 _LIBCPP_HIDE_FROM_ABI constexpr variant& operator=(const variant&) = default;
1238 _LIBCPP_HIDE_FROM_ABI constexpr variant& operator=(variant&&) = default;
1239
1240 template < class _Arg,
1241 enable_if_t<!is_same_v<__remove_cvref_t<_Arg>, variant>, int> = 0,
1242 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1243 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1244 enable_if_t<is_assignable_v<_Tp&, _Arg> && is_constructible_v<_Tp, _Arg>, int> = 0>
1245 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 variant&
1246 operator=(_Arg&& __arg) noexcept(is_nothrow_assignable_v<_Tp&, _Arg> && is_nothrow_constructible_v<_Tp, _Arg>) {
1247 __impl_.template __assign<_Ip>(std::forward<_Arg>(__arg));
1248 return *this;
1249 }
1250
1251 template < size_t _Ip,
1252 class... _Args,
1253 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1254 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1255 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1256 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(_Args&&... __args) {
1257 return __impl_.template __emplace<_Ip>(std::forward<_Args>(__args)...);
1258 }
1259
1260 template < size_t _Ip,
1261 class _Up,
1262 class... _Args,
1263 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1264 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1265 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1266 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1267 return __impl_.template __emplace<_Ip>(__il, std::forward<_Args>(__args)...);
1268 }
1269
1270 template < class _Tp,
1271 class... _Args,
1272 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1273 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1274 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(_Args&&... __args) {
1275 return __impl_.template __emplace<_Ip>(std::forward<_Args>(__args)...);
1276 }
1277
1278 template < class _Tp,
1279 class _Up,
1280 class... _Args,
1281 size_t _Ip = __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1282 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, int> = 0>
1283 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1284 return __impl_.template __emplace<_Ip>(__il, std::forward<_Args>(__args)...);
1285 }
1286
1287 _LIBCPP_HIDE_FROM_ABI constexpr bool valueless_by_exception() const noexcept {
1288 return __impl_.valueless_by_exception();
1289 }
1290
1291 _LIBCPP_HIDE_FROM_ABI constexpr size_t index() const noexcept { return __impl_.index(); }
1292
1293 template < bool _Dummy = true,
1294 enable_if_t< __all<(__dependent_type<is_move_constructible<_Types>, _Dummy>::value &&
1295 __dependent_type<is_swappable<_Types>, _Dummy>::value)...>::value,
1296 int> = 0>
1297 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void swap(variant& __that) noexcept(
1298 __all<(is_nothrow_move_constructible_v<_Types> && is_nothrow_swappable_v<_Types>)...>::value) {
1299 __impl_.__swap(__that.__impl_);
1300 }
1301
1302# if _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
1303 // Helper class to implement [variant.visit]/10
1304 // Constraints: The call to visit does not use an explicit template-argument-list
1305 // that begins with a type template-argument.
1306 struct __variant_visit_barrier_tag {
1307 _LIBCPP_HIDE_FROM_ABI explicit __variant_visit_barrier_tag() = default;
1308 };
1309
1310 template <__variant_visit_barrier_tag = __variant_visit_barrier_tag{}, class _Self, class _Visitor>
1311 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) visit(this _Self&& __self, _Visitor&& __visitor) {
1312 return std::visit(std::forward<_Visitor>(__visitor), std::__forward_as<_Self, variant>(__self));
1313 }
1314
1315 template <class _Rp, class _Self, class _Visitor>
1316 _LIBCPP_HIDE_FROM_ABI constexpr _Rp visit(this _Self&& __self, _Visitor&& __visitor) {
1317 return std::visit<_Rp>(std::forward<_Visitor>(__visitor), std::__forward_as<_Self, variant>(__self));
1318 }
1319# endif
1320
1321private:
1322 __variant_detail::__impl<_Types...> __impl_;
1323
1324 friend struct __variant_detail::__access::__variant;
1325 friend struct __variant_detail::__visitation::__variant;
1326};
1327
1328template <size_t _Ip, class... _Types>
1329_LIBCPP_HIDE_FROM_ABI constexpr bool __holds_alternative(const variant<_Types...>& __v) noexcept {
1330 return __v.index() == _Ip;
1331}
1332
1333template <class _Tp, class... _Types>
1334_LIBCPP_HIDE_FROM_ABI constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept {
1335 return std::__holds_alternative<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1336}
1337
1338template <size_t _Ip, class _Vp>
1339_LIBCPP_HIDE_FROM_ABI constexpr auto&& __generic_get(_Vp&& __v) {
1340 using __variant_detail::__access::__variant;
1341 if (!std::__holds_alternative<_Ip>(__v)) {
1342 std::__throw_bad_variant_access();
1343 }
1344 return __variant::__get_alt<_Ip>(std::forward<_Vp>(__v)).__value;
1345}
1346
1347template <size_t _Ip, class... _Types>
1348_LIBCPP_HIDE_FROM_ABI constexpr variant_alternative_t<_Ip, variant<_Types...>>& get(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>(__v);
1352}
1353
1354template <size_t _Ip, class... _Types>
1355_LIBCPP_HIDE_FROM_ABI constexpr variant_alternative_t<_Ip, variant<_Types...>>&& get(variant<_Types...>&& __v) {
1356 static_assert(_Ip < sizeof...(_Types));
1357 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1358 return std::__generic_get<_Ip>(std::move(__v));
1359}
1360
1361template <size_t _Ip, class... _Types>
1362_LIBCPP_HIDE_FROM_ABI constexpr const variant_alternative_t<_Ip, variant<_Types...>>&
1363get(const variant<_Types...>& __v) {
1364 static_assert(_Ip < sizeof...(_Types));
1365 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1366 return std::__generic_get<_Ip>(__v);
1367}
1368
1369template <size_t _Ip, class... _Types>
1370_LIBCPP_HIDE_FROM_ABI constexpr const variant_alternative_t<_Ip, variant<_Types...>>&&
1371get(const variant<_Types...>&& __v) {
1372 static_assert(_Ip < sizeof...(_Types));
1373 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1374 return std::__generic_get<_Ip>(std::move(__v));
1375}
1376
1377template <class _Tp, class... _Types>
1378_LIBCPP_HIDE_FROM_ABI constexpr _Tp& get(variant<_Types...>& __v) {
1379 static_assert(!is_void_v<_Tp>);
1380 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1381}
1382
1383template <class _Tp, class... _Types>
1384_LIBCPP_HIDE_FROM_ABI constexpr _Tp&& get(variant<_Types...>&& __v) {
1385 static_assert(!is_void_v<_Tp>);
1386 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(std::move(__v));
1387}
1388
1389template <class _Tp, class... _Types>
1390_LIBCPP_HIDE_FROM_ABI constexpr const _Tp& get(const variant<_Types...>& __v) {
1391 static_assert(!is_void_v<_Tp>);
1392 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1393}
1394
1395template <class _Tp, class... _Types>
1396_LIBCPP_HIDE_FROM_ABI constexpr const _Tp&& get(const variant<_Types...>&& __v) {
1397 static_assert(!is_void_v<_Tp>);
1398 return std::get<__find_exactly_one_t<_Tp, _Types...>::value>(std::move(__v));
1399}
1400
1401template <size_t _Ip, class _Vp>
1402_LIBCPP_HIDE_FROM_ABI constexpr auto* __generic_get_if(_Vp* __v) noexcept {
1403 using __variant_detail::__access::__variant;
1404 return __v && std::__holds_alternative<_Ip>(*__v) ? std::addressof(__variant::__get_alt<_Ip>(*__v).__value) : nullptr;
1405}
1406
1407template <size_t _Ip, class... _Types>
1408_LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<variant_alternative_t<_Ip, variant<_Types...>>>
1409get_if(variant<_Types...>* __v) noexcept {
1410 static_assert(_Ip < sizeof...(_Types));
1411 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1412 return std::__generic_get_if<_Ip>(__v);
1413}
1414
1415template <size_t _Ip, class... _Types>
1416_LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<const variant_alternative_t<_Ip, variant<_Types...>>>
1417get_if(const variant<_Types...>* __v) noexcept {
1418 static_assert(_Ip < sizeof...(_Types));
1419 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1420 return std::__generic_get_if<_Ip>(__v);
1421}
1422
1423template <class _Tp, class... _Types>
1424_LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<_Tp> get_if(variant<_Types...>* __v) noexcept {
1425 static_assert(!is_void_v<_Tp>);
1426 return std::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1427}
1428
1429template <class _Tp, class... _Types>
1430_LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<const _Tp> get_if(const variant<_Types...>* __v) noexcept {
1431 static_assert(!is_void_v<_Tp>);
1432 return std::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1433}
1434
1435template <class _Operator>
1436struct __convert_to_bool {
1437 template <class _T1, class _T2>
1438 _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(_T1&& __t1, _T2&& __t2) const {
1439 static_assert(is_convertible<decltype(_Operator{}(std::forward<_T1>(__t1), std::forward<_T2>(__t2))), bool>::value,
1440 "the relational operator does not return a type which is implicitly convertible to bool");
1441 return _Operator{}(std::forward<_T1>(__t1), std::forward<_T2>(__t2));
1442 }
1443};
1444
1445template <class... _Types>
1446# if _LIBCPP_STD_VER >= 26
1447 requires(requires(const _Types& __t) {
1448 { __t == __t } -> __core_convertible_to<bool>;
1449 } && ...)
1450# endif
1451_LIBCPP_HIDE_FROM_ABI constexpr bool operator==(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1452 using __variant_detail::__visitation::__variant;
1453 if (__lhs.index() != __rhs.index())
1454 return false;
1455 if (__lhs.valueless_by_exception())
1456 return true;
1457 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<equal_to<>>{}, __lhs, __rhs);
1458}
1459
1460# if _LIBCPP_STD_VER >= 20
1461
1462template <class... _Types>
1463 requires(three_way_comparable<_Types> && ...)
1464_LIBCPP_HIDE_FROM_ABI constexpr common_comparison_category_t<compare_three_way_result_t<_Types>...>
1465operator<=>(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1466 using __variant_detail::__visitation::__variant;
1467 using __result_t = common_comparison_category_t<compare_three_way_result_t<_Types>...>;
1468 if (__lhs.valueless_by_exception() && __rhs.valueless_by_exception())
1469 return strong_ordering::equal;
1470 if (__lhs.valueless_by_exception())
1471 return strong_ordering::less;
1472 if (__rhs.valueless_by_exception())
1473 return strong_ordering::greater;
1474 if (auto __c = __lhs.index() <=> __rhs.index(); __c != 0)
1475 return __c;
1476 auto __three_way = []<class _Type>(const _Type& __v, const _Type& __w) -> __result_t { return __v <=> __w; };
1477 return __variant::__visit_value_at(__lhs.index(), __three_way, __lhs, __rhs);
1478}
1479
1480# endif // _LIBCPP_STD_VER >= 20
1481
1482template <class... _Types>
1483# if _LIBCPP_STD_VER >= 26
1484 requires(requires(const _Types& __t) {
1485 { __t != __t } -> __core_convertible_to<bool>;
1486 } && ...)
1487# endif
1488_LIBCPP_HIDE_FROM_ABI constexpr bool operator!=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1489 using __variant_detail::__visitation::__variant;
1490 if (__lhs.index() != __rhs.index())
1491 return true;
1492 if (__lhs.valueless_by_exception())
1493 return false;
1494 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<not_equal_to<>>{}, __lhs, __rhs);
1495}
1496
1497template <class... _Types>
1498# if _LIBCPP_STD_VER >= 26
1499 requires(requires(const _Types& __t) {
1500 { __t < __t } -> __core_convertible_to<bool>;
1501 } && ...)
1502# endif
1503_LIBCPP_HIDE_FROM_ABI constexpr bool operator<(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1504 using __variant_detail::__visitation::__variant;
1505 if (__rhs.valueless_by_exception())
1506 return false;
1507 if (__lhs.valueless_by_exception())
1508 return true;
1509 if (__lhs.index() < __rhs.index())
1510 return true;
1511 if (__lhs.index() > __rhs.index())
1512 return false;
1513 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<less<>>{}, __lhs, __rhs);
1514}
1515
1516template <class... _Types>
1517# if _LIBCPP_STD_VER >= 26
1518 requires(requires(const _Types& __t) {
1519 { __t > __t } -> __core_convertible_to<bool>;
1520 } && ...)
1521# endif
1522_LIBCPP_HIDE_FROM_ABI constexpr bool operator>(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1523 using __variant_detail::__visitation::__variant;
1524 if (__lhs.valueless_by_exception())
1525 return false;
1526 if (__rhs.valueless_by_exception())
1527 return true;
1528 if (__lhs.index() > __rhs.index())
1529 return true;
1530 if (__lhs.index() < __rhs.index())
1531 return false;
1532 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<greater<>>{}, __lhs, __rhs);
1533}
1534
1535template <class... _Types>
1536# if _LIBCPP_STD_VER >= 26
1537 requires(requires(const _Types& __t) {
1538 { __t <= __t } -> __core_convertible_to<bool>;
1539 } && ...)
1540# endif
1541_LIBCPP_HIDE_FROM_ABI constexpr bool operator<=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1542 using __variant_detail::__visitation::__variant;
1543 if (__lhs.valueless_by_exception())
1544 return true;
1545 if (__rhs.valueless_by_exception())
1546 return false;
1547 if (__lhs.index() < __rhs.index())
1548 return true;
1549 if (__lhs.index() > __rhs.index())
1550 return false;
1551 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<less_equal<>>{}, __lhs, __rhs);
1552}
1553
1554template <class... _Types>
1555# if _LIBCPP_STD_VER >= 26
1556 requires(requires(const _Types& __t) {
1557 { __t >= __t } -> __core_convertible_to<bool>;
1558 } && ...)
1559# endif
1560_LIBCPP_HIDE_FROM_ABI constexpr bool operator>=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs) {
1561 using __variant_detail::__visitation::__variant;
1562 if (__rhs.valueless_by_exception())
1563 return true;
1564 if (__lhs.valueless_by_exception())
1565 return false;
1566 if (__lhs.index() > __rhs.index())
1567 return true;
1568 if (__lhs.index() < __rhs.index())
1569 return false;
1570 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<greater_equal<>>{}, __lhs, __rhs);
1571}
1572
1573template <class... _Vs>
1574_LIBCPP_HIDE_FROM_ABI constexpr void __throw_if_valueless(_Vs&&... __vs) {
1575 const bool __valueless = (... || std::__as_variant(__vs).valueless_by_exception());
1576 if (__valueless) {
1577 std::__throw_bad_variant_access();
1578 }
1579}
1580
1581template < class _Visitor, class... _Vs, typename>
1582_LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
1583 using __variant_detail::__visitation::__variant;
1584 std::__throw_if_valueless(std::forward<_Vs>(__vs)...);
1585 return __variant::__visit_value(std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs)...);
1586}
1587
1588# if _LIBCPP_STD_VER >= 20
1589template < class _Rp, class _Visitor, class... _Vs, typename>
1590_LIBCPP_HIDE_FROM_ABI constexpr _Rp visit(_Visitor&& __visitor, _Vs&&... __vs) {
1591 using __variant_detail::__visitation::__variant;
1592 std::__throw_if_valueless(std::forward<_Vs>(__vs)...);
1593 return __variant::__visit_value<_Rp>(std::forward<_Visitor>(__visitor), std::forward<_Vs>(__vs)...);
1594}
1595# endif
1596
1597template <class... _Types>
1598_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 auto
1599swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs)))
1600 -> decltype(__lhs.swap(__rhs)) {
1601 return __lhs.swap(__rhs);
1602}
1603
1604template <class... _Types>
1605struct hash< __enable_hash_helper<variant<_Types...>, remove_const_t<_Types>...>> {
1606# if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
1607 using argument_type _LIBCPP_DEPRECATED_IN_CXX17 = variant<_Types...>;
1608 using result_type _LIBCPP_DEPRECATED_IN_CXX17 = size_t;
1609# endif
1610
1611 _LIBCPP_HIDE_FROM_ABI size_t operator()(const variant<_Types...>& __v) const {
1612 using __variant_detail::__visitation::__variant;
1613 size_t __res =
1614 __v.valueless_by_exception()
1615 ? 299792458 // Random value chosen by the universe upon creation
1616 : __variant::__visit_alt(
1617 [](const auto& __alt) {
1618 using __alt_type = __remove_cvref_t<decltype(__alt)>;
1619 using __value_type = remove_const_t< typename __alt_type::__value_type>;
1620 return hash<__value_type>{}(__alt.__value);
1621 },
1622 __v);
1623 return std::__hash_combine(__res, hash<size_t>{}(__v.index()));
1624 }
1625};
1626
1627// __unchecked_get is the same as std::get, except, it is UB to use it with the wrong
1628// type whereas std::get will throw or returning nullptr. This makes it faster than
1629// std::get.
1630template <size_t _Ip, class _Vp>
1631_LIBCPP_HIDE_FROM_ABI constexpr auto&& __unchecked_get(_Vp&& __v) noexcept {
1632 using __variant_detail::__access::__variant;
1633 return __variant::__get_alt<_Ip>(std::forward<_Vp>(__v)).__value;
1634}
1635
1636template <class _Tp, class... _Types>
1637_LIBCPP_HIDE_FROM_ABI constexpr auto&& __unchecked_get(const variant<_Types...>& __v) noexcept {
1638 return std::__unchecked_get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1639}
1640
1641template <class _Tp, class... _Types>
1642_LIBCPP_HIDE_FROM_ABI constexpr auto&& __unchecked_get(variant<_Types...>& __v) noexcept {
1643 return std::__unchecked_get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1644}
1645
1646# endif // _LIBCPP_STD_VER >= 17
1647
1648_LIBCPP_END_NAMESPACE_STD
1649
1650_LIBCPP_POP_MACROS
1651
1652# if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
1653# include <cstddef>
1654# include <exception>
1655# include <tuple>
1656# include <type_traits>
1657# include <typeinfo>
1658# include <utility>
1659# endif
1660#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
1661
1662#endif // _LIBCPP_VARIANT