1// -*- C++ -*-
2//===------------------------------ variant -------------------------------===//
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 variant(const variant&); // constexpr in C++20
26 variant(variant&&) noexcept(see below); // constexpr in C++20
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 ~variant();
46
47 // 20.7.2.3, assignment
48 variant& operator=(const variant&); // constexpr in C++20
49 variant& operator=(variant&&) noexcept(see below); // constexpr in C++20
50
51 template <class T> variant& operator=(T&&) noexcept(see below);
52
53 // 20.7.2.4, modifiers
54 template <class T, class... Args>
55 T& emplace(Args&&...);
56
57 template <class T, class U, class... Args>
58 T& emplace(initializer_list<U>, Args&&...);
59
60 template <size_t I, class... Args>
61 variant_alternative_t<I, variant>& emplace(Args&&...);
62
63 template <size_t I, class U, class... Args>
64 variant_alternative_t<I, variant>& emplace(initializer_list<U>, Args&&...);
65
66 // 20.7.2.5, value status
67 constexpr bool valueless_by_exception() const noexcept;
68 constexpr size_t index() const noexcept;
69
70 // 20.7.2.6, swap
71 void swap(variant&) noexcept(see below);
72 };
73
74 // 20.7.3, variant helper classes
75 template <class T> struct variant_size; // undefined
76
77 template <class T>
78 inline constexpr size_t variant_size_v = variant_size<T>::value;
79
80 template <class T> struct variant_size<const T>;
81 template <class T> struct variant_size<volatile T>;
82 template <class T> struct variant_size<const volatile T>;
83
84 template <class... Types>
85 struct variant_size<variant<Types...>>;
86
87 template <size_t I, class T> struct variant_alternative; // undefined
88
89 template <size_t I, class T>
90 using variant_alternative_t = typename variant_alternative<I, T>::type;
91
92 template <size_t I, class T> struct variant_alternative<I, const T>;
93 template <size_t I, class T> struct variant_alternative<I, volatile T>;
94 template <size_t I, class T> struct variant_alternative<I, const volatile T>;
95
96 template <size_t I, class... Types>
97 struct variant_alternative<I, variant<Types...>>;
98
99 inline constexpr size_t variant_npos = -1;
100
101 // 20.7.4, value access
102 template <class T, class... Types>
103 constexpr bool holds_alternative(const variant<Types...>&) noexcept;
104
105 template <size_t I, class... Types>
106 constexpr variant_alternative_t<I, variant<Types...>>&
107 get(variant<Types...>&);
108
109 template <size_t I, class... Types>
110 constexpr variant_alternative_t<I, variant<Types...>>&&
111 get(variant<Types...>&&);
112
113 template <size_t I, class... Types>
114 constexpr variant_alternative_t<I, variant<Types...>> const&
115 get(const variant<Types...>&);
116
117 template <size_t I, class... Types>
118 constexpr variant_alternative_t<I, variant<Types...>> const&&
119 get(const variant<Types...>&&);
120
121 template <class T, class... Types>
122 constexpr T& get(variant<Types...>&);
123
124 template <class T, class... Types>
125 constexpr T&& get(variant<Types...>&&);
126
127 template <class T, class... Types>
128 constexpr const T& get(const variant<Types...>&);
129
130 template <class T, class... Types>
131 constexpr const T&& get(const variant<Types...>&&);
132
133 template <size_t I, class... Types>
134 constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>>
135 get_if(variant<Types...>*) noexcept;
136
137 template <size_t I, class... Types>
138 constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>>
139 get_if(const variant<Types...>*) noexcept;
140
141 template <class T, class... Types>
142 constexpr add_pointer_t<T>
143 get_if(variant<Types...>*) noexcept;
144
145 template <class T, class... Types>
146 constexpr add_pointer_t<const T>
147 get_if(const variant<Types...>*) noexcept;
148
149 // 20.7.5, relational operators
150 template <class... Types>
151 constexpr bool operator==(const variant<Types...>&, const variant<Types...>&);
152
153 template <class... Types>
154 constexpr bool operator!=(const variant<Types...>&, const variant<Types...>&);
155
156 template <class... Types>
157 constexpr bool operator<(const variant<Types...>&, const variant<Types...>&);
158
159 template <class... Types>
160 constexpr bool operator>(const variant<Types...>&, const variant<Types...>&);
161
162 template <class... Types>
163 constexpr bool operator<=(const variant<Types...>&, const variant<Types...>&);
164
165 template <class... Types>
166 constexpr bool operator>=(const variant<Types...>&, const variant<Types...>&);
167
168 // 20.7.6, visitation
169 template <class Visitor, class... Variants>
170 constexpr see below visit(Visitor&&, Variants&&...);
171
172 // 20.7.7, class monostate
173 struct monostate;
174
175 // 20.7.8, monostate relational operators
176 constexpr bool operator<(monostate, monostate) noexcept;
177 constexpr bool operator>(monostate, monostate) noexcept;
178 constexpr bool operator<=(monostate, monostate) noexcept;
179 constexpr bool operator>=(monostate, monostate) noexcept;
180 constexpr bool operator==(monostate, monostate) noexcept;
181 constexpr bool operator!=(monostate, monostate) noexcept;
182
183 // 20.7.9, specialized algorithms
184 template <class... Types>
185 void swap(variant<Types...>&, variant<Types...>&) noexcept(see below);
186
187 // 20.7.10, class bad_variant_access
188 class bad_variant_access;
189
190 // 20.7.11, hash support
191 template <class T> struct hash;
192 template <class... Types> struct hash<variant<Types...>>;
193 template <> struct hash<monostate>;
194
195} // namespace std
196
197*/
198
199#include <__config>
200#include <__tuple>
201#include <array>
202#include <exception>
203#include <functional>
204#include <initializer_list>
205#include <new>
206#include <tuple>
207#include <type_traits>
208#include <utility>
209#include <limits>
210#include <version>
211
212#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
213#pragma GCC system_header
214#endif
215
216_LIBCPP_PUSH_MACROS
217#include <__undef_macros>
218
219namespace std { // explicitly not using versioning namespace
220
221class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS bad_variant_access : public exception {
222public:
223 virtual const char* what() const _NOEXCEPT;
224};
225
226} // namespace std
227
228_LIBCPP_BEGIN_NAMESPACE_STD
229
230#if _LIBCPP_STD_VER > 14
231
232_LIBCPP_NORETURN
233inline _LIBCPP_INLINE_VISIBILITY
234_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
235void __throw_bad_variant_access() {
236#ifndef _LIBCPP_NO_EXCEPTIONS
237 throw bad_variant_access();
238#else
239 _VSTD::abort();
240#endif
241}
242
243template <class... _Types>
244class _LIBCPP_TEMPLATE_VIS variant;
245
246template <class _Tp>
247struct _LIBCPP_TEMPLATE_VIS variant_size;
248
249template <class _Tp>
250_LIBCPP_INLINE_VAR constexpr size_t variant_size_v = variant_size<_Tp>::value;
251
252template <class _Tp>
253struct _LIBCPP_TEMPLATE_VIS variant_size<const _Tp> : variant_size<_Tp> {};
254
255template <class _Tp>
256struct _LIBCPP_TEMPLATE_VIS variant_size<volatile _Tp> : variant_size<_Tp> {};
257
258template <class _Tp>
259struct _LIBCPP_TEMPLATE_VIS variant_size<const volatile _Tp>
260 : variant_size<_Tp> {};
261
262template <class... _Types>
263struct _LIBCPP_TEMPLATE_VIS variant_size<variant<_Types...>>
264 : integral_constant<size_t, sizeof...(_Types)> {};
265
266template <size_t _Ip, class _Tp>
267struct _LIBCPP_TEMPLATE_VIS variant_alternative;
268
269template <size_t _Ip, class _Tp>
270using variant_alternative_t = typename variant_alternative<_Ip, _Tp>::type;
271
272template <size_t _Ip, class _Tp>
273struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const _Tp>
274 : add_const<variant_alternative_t<_Ip, _Tp>> {};
275
276template <size_t _Ip, class _Tp>
277struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, volatile _Tp>
278 : add_volatile<variant_alternative_t<_Ip, _Tp>> {};
279
280template <size_t _Ip, class _Tp>
281struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const volatile _Tp>
282 : add_cv<variant_alternative_t<_Ip, _Tp>> {};
283
284template <size_t _Ip, class... _Types>
285struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, variant<_Types...>> {
286 static_assert(_Ip < sizeof...(_Types), "Index out of bounds in std::variant_alternative<>");
287 using type = __type_pack_element<_Ip, _Types...>;
288};
289
290_LIBCPP_INLINE_VAR constexpr size_t variant_npos = static_cast<size_t>(-1);
291
292constexpr int __choose_index_type(unsigned int __num_elem) {
293 if (__num_elem < std::numeric_limits<unsigned char>::max())
294 return 0;
295 if (__num_elem < std::numeric_limits<unsigned short>::max())
296 return 1;
297 return 2;
298}
299
300template <size_t _NumAlts>
301using __variant_index_t =
302#ifndef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
303 unsigned int;
304#else
305 std::tuple_element_t<
306 __choose_index_type(_NumAlts),
307 std::tuple<unsigned char, unsigned short, unsigned int>
308 >;
309#endif
310
311template <class _IndexType>
312constexpr _IndexType __variant_npos = static_cast<_IndexType>(-1);
313
314namespace __find_detail {
315
316template <class _Tp, class... _Types>
317inline _LIBCPP_INLINE_VISIBILITY
318constexpr size_t __find_index() {
319 constexpr bool __matches[] = {is_same_v<_Tp, _Types>...};
320 size_t __result = __not_found;
321 for (size_t __i = 0; __i < sizeof...(_Types); ++__i) {
322 if (__matches[__i]) {
323 if (__result != __not_found) {
324 return __ambiguous;
325 }
326 __result = __i;
327 }
328 }
329 return __result;
330}
331
332template <size_t _Index>
333struct __find_unambiguous_index_sfinae_impl
334 : integral_constant<size_t, _Index> {};
335
336template <>
337struct __find_unambiguous_index_sfinae_impl<__not_found> {};
338
339template <>
340struct __find_unambiguous_index_sfinae_impl<__ambiguous> {};
341
342template <class _Tp, class... _Types>
343struct __find_unambiguous_index_sfinae
344 : __find_unambiguous_index_sfinae_impl<__find_index<_Tp, _Types...>()> {};
345
346} // namespace __find_detail
347
348namespace __variant_detail {
349
350struct __valueless_t {};
351
352enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
353
354template <typename _Tp,
355 template <typename> class _IsTriviallyAvailable,
356 template <typename> class _IsAvailable>
357constexpr _Trait __trait =
358 _IsTriviallyAvailable<_Tp>::value
359 ? _Trait::_TriviallyAvailable
360 : _IsAvailable<_Tp>::value ? _Trait::_Available : _Trait::_Unavailable;
361
362inline _LIBCPP_INLINE_VISIBILITY
363constexpr _Trait __common_trait(initializer_list<_Trait> __traits) {
364 _Trait __result = _Trait::_TriviallyAvailable;
365 for (_Trait __t : __traits) {
366 if (static_cast<int>(__t) > static_cast<int>(__result)) {
367 __result = __t;
368 }
369 }
370 return __result;
371}
372
373template <typename... _Types>
374struct __traits {
375 static constexpr _Trait __copy_constructible_trait =
376 __common_trait({__trait<_Types,
377 is_trivially_copy_constructible,
378 is_copy_constructible>...});
379
380 static constexpr _Trait __move_constructible_trait =
381 __common_trait({__trait<_Types,
382 is_trivially_move_constructible,
383 is_move_constructible>...});
384
385 static constexpr _Trait __copy_assignable_trait = __common_trait(
386 {__copy_constructible_trait,
387 __trait<_Types, is_trivially_copy_assignable, is_copy_assignable>...});
388
389 static constexpr _Trait __move_assignable_trait = __common_trait(
390 {__move_constructible_trait,
391 __trait<_Types, is_trivially_move_assignable, is_move_assignable>...});
392
393 static constexpr _Trait __destructible_trait = __common_trait(
394 {__trait<_Types, is_trivially_destructible, is_destructible>...});
395};
396
397namespace __access {
398
399struct __union {
400 template <class _Vp>
401 inline _LIBCPP_INLINE_VISIBILITY
402 static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<0>) {
403 return _VSTD::forward<_Vp>(__v).__head;
404 }
405
406 template <class _Vp, size_t _Ip>
407 inline _LIBCPP_INLINE_VISIBILITY
408 static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<_Ip>) {
409 return __get_alt(_VSTD::forward<_Vp>(__v).__tail, in_place_index<_Ip - 1>);
410 }
411};
412
413struct __base {
414 template <size_t _Ip, class _Vp>
415 inline _LIBCPP_INLINE_VISIBILITY
416 static constexpr auto&& __get_alt(_Vp&& __v) {
417 return __union::__get_alt(_VSTD::forward<_Vp>(__v).__data,
418 in_place_index<_Ip>);
419 }
420};
421
422struct __variant {
423 template <size_t _Ip, class _Vp>
424 inline _LIBCPP_INLINE_VISIBILITY
425 static constexpr auto&& __get_alt(_Vp&& __v) {
426 return __base::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v).__impl);
427 }
428};
429
430} // namespace __access
431
432namespace __visitation {
433
434struct __base {
435 template <class _Visitor, class... _Vs>
436 inline _LIBCPP_INLINE_VISIBILITY
437 static constexpr decltype(auto)
438 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
439 constexpr auto __fdiagonal =
440 __make_fdiagonal<_Visitor&&,
441 decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
442 return __fdiagonal[__index](_VSTD::forward<_Visitor>(__visitor),
443 _VSTD::forward<_Vs>(__vs).__as_base()...);
444 }
445
446 template <class _Visitor, class... _Vs>
447 inline _LIBCPP_INLINE_VISIBILITY
448 static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
449 _Vs&&... __vs) {
450 constexpr auto __fmatrix =
451 __make_fmatrix<_Visitor&&,
452 decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
453 return __at(__fmatrix, __vs.index()...)(
454 _VSTD::forward<_Visitor>(__visitor),
455 _VSTD::forward<_Vs>(__vs).__as_base()...);
456 }
457
458private:
459 template <class _Tp>
460 inline _LIBCPP_INLINE_VISIBILITY
461 static constexpr const _Tp& __at(const _Tp& __elem) { return __elem; }
462
463 template <class _Tp, size_t _Np, typename... _Indices>
464 inline _LIBCPP_INLINE_VISIBILITY
465 static constexpr auto&& __at(const array<_Tp, _Np>& __elems,
466 size_t __index, _Indices... __indices) {
467 return __at(__elems[__index], __indices...);
468 }
469
470 template <class _Fp, class... _Fs>
471 static constexpr void __std_visit_visitor_return_type_check() {
472 static_assert(
473 __all<is_same_v<_Fp, _Fs>...>::value,
474 "`std::visit` requires the visitor to have a single return type.");
475 }
476
477 template <class... _Fs>
478 inline _LIBCPP_INLINE_VISIBILITY
479 static constexpr auto __make_farray(_Fs&&... __fs) {
480 __std_visit_visitor_return_type_check<__uncvref_t<_Fs>...>();
481 using __result = array<common_type_t<__uncvref_t<_Fs>...>, sizeof...(_Fs)>;
482 return __result{{_VSTD::forward<_Fs>(__fs)...}};
483 }
484
485 template <std::size_t... _Is>
486 struct __dispatcher {
487 template <class _Fp, class... _Vs>
488 inline _LIBCPP_INLINE_VISIBILITY
489 static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
490 return __invoke_constexpr(
491 static_cast<_Fp>(__f),
492 __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
493 }
494 };
495
496 template <class _Fp, class... _Vs, size_t... _Is>
497 inline _LIBCPP_INLINE_VISIBILITY
498 static constexpr auto __make_dispatch(index_sequence<_Is...>) {
499 return __dispatcher<_Is...>::template __dispatch<_Fp, _Vs...>;
500 }
501
502 template <size_t _Ip, class _Fp, class... _Vs>
503 inline _LIBCPP_INLINE_VISIBILITY
504 static constexpr auto __make_fdiagonal_impl() {
505 return __make_dispatch<_Fp, _Vs...>(
506 index_sequence<(__identity<_Vs>{}, _Ip)...>{});
507 }
508
509 template <class _Fp, class... _Vs, size_t... _Is>
510 inline _LIBCPP_INLINE_VISIBILITY
511 static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
512 return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
513 }
514
515 template <class _Fp, class _Vp, class... _Vs>
516 inline _LIBCPP_INLINE_VISIBILITY
517 static constexpr auto __make_fdiagonal() {
518 constexpr size_t _Np = __uncvref_t<_Vp>::__size();
519 static_assert(__all<(_Np == __uncvref_t<_Vs>::__size())...>::value);
520 return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<_Np>{});
521 }
522
523 template <class _Fp, class... _Vs, size_t... _Is>
524 inline _LIBCPP_INLINE_VISIBILITY
525 static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
526 return __make_dispatch<_Fp, _Vs...>(__is);
527 }
528
529 template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
530 inline _LIBCPP_INLINE_VISIBILITY
531 static constexpr auto __make_fmatrix_impl(index_sequence<_Is...>,
532 index_sequence<_Js...>,
533 _Ls... __ls) {
534 return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(
535 index_sequence<_Is..., _Js>{}, __ls...)...);
536 }
537
538 template <class _Fp, class... _Vs>
539 inline _LIBCPP_INLINE_VISIBILITY
540 static constexpr auto __make_fmatrix() {
541 return __make_fmatrix_impl<_Fp, _Vs...>(
542 index_sequence<>{}, make_index_sequence<__uncvref_t<_Vs>::__size()>{}...);
543 }
544};
545
546struct __variant {
547 template <class _Visitor, class... _Vs>
548 inline _LIBCPP_INLINE_VISIBILITY
549 static constexpr decltype(auto)
550 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
551 return __base::__visit_alt_at(__index,
552 _VSTD::forward<_Visitor>(__visitor),
553 _VSTD::forward<_Vs>(__vs).__impl...);
554 }
555
556 template <class _Visitor, class... _Vs>
557 inline _LIBCPP_INLINE_VISIBILITY
558 static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
559 _Vs&&... __vs) {
560 return __base::__visit_alt(_VSTD::forward<_Visitor>(__visitor),
561 _VSTD::forward<_Vs>(__vs).__impl...);
562 }
563
564 template <class _Visitor, class... _Vs>
565 inline _LIBCPP_INLINE_VISIBILITY
566 static constexpr decltype(auto)
567 __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
568 return __visit_alt_at(
569 __index,
570 __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
571 _VSTD::forward<_Vs>(__vs)...);
572 }
573
574 template <class _Visitor, class... _Vs>
575 inline _LIBCPP_INLINE_VISIBILITY
576 static constexpr decltype(auto) __visit_value(_Visitor&& __visitor,
577 _Vs&&... __vs) {
578 return __visit_alt(
579 __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
580 _VSTD::forward<_Vs>(__vs)...);
581 }
582
583private:
584 template <class _Visitor, class... _Values>
585 static constexpr void __std_visit_exhaustive_visitor_check() {
586 static_assert(is_invocable_v<_Visitor, _Values...>,
587 "`std::visit` requires the visitor to be exhaustive.");
588 }
589
590 template <class _Visitor>
591 struct __value_visitor {
592 template <class... _Alts>
593 inline _LIBCPP_INLINE_VISIBILITY
594 constexpr decltype(auto) operator()(_Alts&&... __alts) const {
595 __std_visit_exhaustive_visitor_check<
596 _Visitor,
597 decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
598 return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor),
599 _VSTD::forward<_Alts>(__alts).__value...);
600 }
601 _Visitor&& __visitor;
602 };
603
604 template <class _Visitor>
605 inline _LIBCPP_INLINE_VISIBILITY
606 static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
607 return __value_visitor<_Visitor>{_VSTD::forward<_Visitor>(__visitor)};
608 }
609};
610
611} // namespace __visitation
612
613template <size_t _Index, class _Tp>
614struct _LIBCPP_TEMPLATE_VIS __alt {
615 using __value_type = _Tp;
616
617 template <class... _Args>
618 inline _LIBCPP_INLINE_VISIBILITY
619 explicit constexpr __alt(in_place_t, _Args&&... __args)
620 : __value(_VSTD::forward<_Args>(__args)...) {}
621
622 __value_type __value;
623};
624
625template <_Trait _DestructibleTrait, size_t _Index, class... _Types>
626union _LIBCPP_TEMPLATE_VIS __union;
627
628template <_Trait _DestructibleTrait, size_t _Index>
629union _LIBCPP_TEMPLATE_VIS __union<_DestructibleTrait, _Index> {};
630
631#define _LIBCPP_VARIANT_UNION(destructible_trait, destructor) \
632 template <size_t _Index, class _Tp, class... _Types> \
633 union _LIBCPP_TEMPLATE_VIS __union<destructible_trait, \
634 _Index, \
635 _Tp, \
636 _Types...> { \
637 public: \
638 inline _LIBCPP_INLINE_VISIBILITY \
639 explicit constexpr __union(__valueless_t) noexcept : __dummy{} {} \
640 \
641 template <class... _Args> \
642 inline _LIBCPP_INLINE_VISIBILITY \
643 explicit constexpr __union(in_place_index_t<0>, _Args&&... __args) \
644 : __head(in_place, _VSTD::forward<_Args>(__args)...) {} \
645 \
646 template <size_t _Ip, class... _Args> \
647 inline _LIBCPP_INLINE_VISIBILITY \
648 explicit constexpr __union(in_place_index_t<_Ip>, _Args&&... __args) \
649 : __tail(in_place_index<_Ip - 1>, _VSTD::forward<_Args>(__args)...) {} \
650 \
651 __union(const __union&) = default; \
652 __union(__union&&) = default; \
653 \
654 destructor \
655 \
656 __union& operator=(const __union&) = default; \
657 __union& operator=(__union&&) = default; \
658 \
659 private: \
660 char __dummy; \
661 __alt<_Index, _Tp> __head; \
662 __union<destructible_trait, _Index + 1, _Types...> __tail; \
663 \
664 friend struct __access::__union; \
665 }
666
667_LIBCPP_VARIANT_UNION(_Trait::_TriviallyAvailable, ~__union() = default;);
668_LIBCPP_VARIANT_UNION(_Trait::_Available, ~__union() {});
669_LIBCPP_VARIANT_UNION(_Trait::_Unavailable, ~__union() = delete;);
670
671#undef _LIBCPP_VARIANT_UNION
672
673template <_Trait _DestructibleTrait, class... _Types>
674class _LIBCPP_TEMPLATE_VIS __base {
675public:
676 using __index_t = __variant_index_t<sizeof...(_Types)>;
677
678 inline _LIBCPP_INLINE_VISIBILITY
679 explicit constexpr __base(__valueless_t tag) noexcept
680 : __data(tag), __index(__variant_npos<__index_t>) {}
681
682 template <size_t _Ip, class... _Args>
683 inline _LIBCPP_INLINE_VISIBILITY
684 explicit constexpr __base(in_place_index_t<_Ip>, _Args&&... __args)
685 :
686 __data(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...),
687 __index(_Ip) {}
688
689 inline _LIBCPP_INLINE_VISIBILITY
690 constexpr bool valueless_by_exception() const noexcept {
691 return index() == variant_npos;
692 }
693
694 inline _LIBCPP_INLINE_VISIBILITY
695 constexpr size_t index() const noexcept {
696 return __index == __variant_npos<__index_t> ? variant_npos : __index;
697 }
698
699protected:
700 inline _LIBCPP_INLINE_VISIBILITY
701 constexpr auto&& __as_base() & { return *this; }
702
703 inline _LIBCPP_INLINE_VISIBILITY
704 constexpr auto&& __as_base() && { return _VSTD::move(*this); }
705
706 inline _LIBCPP_INLINE_VISIBILITY
707 constexpr auto&& __as_base() const & { return *this; }
708
709 inline _LIBCPP_INLINE_VISIBILITY
710 constexpr auto&& __as_base() const && { return _VSTD::move(*this); }
711
712 inline _LIBCPP_INLINE_VISIBILITY
713 static constexpr size_t __size() { return sizeof...(_Types); }
714
715 __union<_DestructibleTrait, 0, _Types...> __data;
716 __index_t __index;
717
718 friend struct __access::__base;
719 friend struct __visitation::__base;
720};
721
722template <class _Traits, _Trait = _Traits::__destructible_trait>
723class _LIBCPP_TEMPLATE_VIS __destructor;
724
725#define _LIBCPP_VARIANT_DESTRUCTOR(destructible_trait, destructor, destroy) \
726 template <class... _Types> \
727 class _LIBCPP_TEMPLATE_VIS __destructor<__traits<_Types...>, \
728 destructible_trait> \
729 : public __base<destructible_trait, _Types...> { \
730 using __base_type = __base<destructible_trait, _Types...>; \
731 using __index_t = typename __base_type::__index_t; \
732 \
733 public: \
734 using __base_type::__base_type; \
735 using __base_type::operator=; \
736 \
737 __destructor(const __destructor&) = default; \
738 __destructor(__destructor&&) = default; \
739 destructor \
740 __destructor& operator=(const __destructor&) = default; \
741 __destructor& operator=(__destructor&&) = default; \
742 \
743 protected: \
744 inline _LIBCPP_INLINE_VISIBILITY \
745 destroy \
746 }
747
748_LIBCPP_VARIANT_DESTRUCTOR(
749 _Trait::_TriviallyAvailable,
750 ~__destructor() = default;,
751 void __destroy() noexcept { this->__index = __variant_npos<__index_t>; });
752
753_LIBCPP_VARIANT_DESTRUCTOR(
754 _Trait::_Available,
755 ~__destructor() { __destroy(); },
756 void __destroy() noexcept {
757 if (!this->valueless_by_exception()) {
758 __visitation::__base::__visit_alt(
759 [](auto& __alt) noexcept {
760 using __alt_type = __uncvref_t<decltype(__alt)>;
761 __alt.~__alt_type();
762 },
763 *this);
764 }
765 this->__index = __variant_npos<__index_t>;
766 });
767
768_LIBCPP_VARIANT_DESTRUCTOR(
769 _Trait::_Unavailable,
770 ~__destructor() = delete;,
771 void __destroy() noexcept = delete;);
772
773#undef _LIBCPP_VARIANT_DESTRUCTOR
774
775template <class _Traits>
776class _LIBCPP_TEMPLATE_VIS __constructor : public __destructor<_Traits> {
777 using __base_type = __destructor<_Traits>;
778
779public:
780 using __base_type::__base_type;
781 using __base_type::operator=;
782
783protected:
784 template <size_t _Ip, class _Tp, class... _Args>
785 inline _LIBCPP_INLINE_VISIBILITY
786 static _Tp& __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) {
787 ::new ((void*)_VSTD::addressof(__a))
788 __alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
789 return __a.__value;
790 }
791
792 template <class _Rhs>
793 inline _LIBCPP_INLINE_VISIBILITY
794 static void __generic_construct(__constructor& __lhs, _Rhs&& __rhs) {
795 __lhs.__destroy();
796 if (!__rhs.valueless_by_exception()) {
797 __visitation::__base::__visit_alt_at(
798 __rhs.index(),
799 [](auto& __lhs_alt, auto&& __rhs_alt) {
800 __construct_alt(
801 __lhs_alt,
802 _VSTD::forward<decltype(__rhs_alt)>(__rhs_alt).__value);
803 },
804 __lhs, _VSTD::forward<_Rhs>(__rhs));
805 __lhs.__index = __rhs.index();
806 }
807 }
808};
809
810template <class _Traits, _Trait = _Traits::__move_constructible_trait>
811class _LIBCPP_TEMPLATE_VIS __move_constructor;
812
813#define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, \
814 move_constructor) \
815 template <class... _Types> \
816 class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \
817 move_constructible_trait> \
818 : public __constructor<__traits<_Types...>> { \
819 using __base_type = __constructor<__traits<_Types...>>; \
820 \
821 public: \
822 using __base_type::__base_type; \
823 using __base_type::operator=; \
824 \
825 __move_constructor(const __move_constructor&) = default; \
826 move_constructor \
827 ~__move_constructor() = default; \
828 __move_constructor& operator=(const __move_constructor&) = default; \
829 __move_constructor& operator=(__move_constructor&&) = default; \
830 }
831
832_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
833 _Trait::_TriviallyAvailable,
834 __move_constructor(__move_constructor&& __that) = default;);
835
836_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
837 _Trait::_Available,
838 __move_constructor(__move_constructor&& __that) noexcept(
839 __all<is_nothrow_move_constructible_v<_Types>...>::value)
840 : __move_constructor(__valueless_t{}) {
841 this->__generic_construct(*this, _VSTD::move(__that));
842 });
843
844_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
845 _Trait::_Unavailable,
846 __move_constructor(__move_constructor&&) = delete;);
847
848#undef _LIBCPP_VARIANT_MOVE_CONSTRUCTOR
849
850template <class _Traits, _Trait = _Traits::__copy_constructible_trait>
851class _LIBCPP_TEMPLATE_VIS __copy_constructor;
852
853#define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, \
854 copy_constructor) \
855 template <class... _Types> \
856 class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>, \
857 copy_constructible_trait> \
858 : public __move_constructor<__traits<_Types...>> { \
859 using __base_type = __move_constructor<__traits<_Types...>>; \
860 \
861 public: \
862 using __base_type::__base_type; \
863 using __base_type::operator=; \
864 \
865 copy_constructor \
866 __copy_constructor(__copy_constructor&&) = default; \
867 ~__copy_constructor() = default; \
868 __copy_constructor& operator=(const __copy_constructor&) = default; \
869 __copy_constructor& operator=(__copy_constructor&&) = default; \
870 }
871
872_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
873 _Trait::_TriviallyAvailable,
874 __copy_constructor(const __copy_constructor& __that) = default;);
875
876_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
877 _Trait::_Available,
878 __copy_constructor(const __copy_constructor& __that)
879 : __copy_constructor(__valueless_t{}) {
880 this->__generic_construct(*this, __that);
881 });
882
883_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
884 _Trait::_Unavailable,
885 __copy_constructor(const __copy_constructor&) = delete;);
886
887#undef _LIBCPP_VARIANT_COPY_CONSTRUCTOR
888
889template <class _Traits>
890class _LIBCPP_TEMPLATE_VIS __assignment : public __copy_constructor<_Traits> {
891 using __base_type = __copy_constructor<_Traits>;
892
893public:
894 using __base_type::__base_type;
895 using __base_type::operator=;
896
897 template <size_t _Ip, class... _Args>
898 inline _LIBCPP_INLINE_VISIBILITY
899 auto& __emplace(_Args&&... __args) {
900 this->__destroy();
901 auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
902 _VSTD::forward<_Args>(__args)...);
903 this->__index = _Ip;
904 return __res;
905 }
906
907protected:
908 template <size_t _Ip, class _Tp, class _Arg>
909 inline _LIBCPP_INLINE_VISIBILITY
910 void __assign_alt(__alt<_Ip, _Tp>& __a, _Arg&& __arg) {
911 if (this->index() == _Ip) {
912 __a.__value = _VSTD::forward<_Arg>(__arg);
913 } else {
914 struct {
915 void operator()(true_type) const {
916 __this->__emplace<_Ip>(_VSTD::forward<_Arg>(__arg));
917 }
918 void operator()(false_type) const {
919 __this->__emplace<_Ip>(_Tp(_VSTD::forward<_Arg>(__arg)));
920 }
921 __assignment* __this;
922 _Arg&& __arg;
923 } __impl{this, _VSTD::forward<_Arg>(__arg)};
924 __impl(bool_constant<is_nothrow_constructible_v<_Tp, _Arg> ||
925 !is_nothrow_move_constructible_v<_Tp>>{});
926 }
927 }
928
929 template <class _That>
930 inline _LIBCPP_INLINE_VISIBILITY
931 void __generic_assign(_That&& __that) {
932 if (this->valueless_by_exception() && __that.valueless_by_exception()) {
933 // do nothing.
934 } else if (__that.valueless_by_exception()) {
935 this->__destroy();
936 } else {
937 __visitation::__base::__visit_alt_at(
938 __that.index(),
939 [this](auto& __this_alt, auto&& __that_alt) {
940 this->__assign_alt(
941 __this_alt,
942 _VSTD::forward<decltype(__that_alt)>(__that_alt).__value);
943 },
944 *this, _VSTD::forward<_That>(__that));
945 }
946 }
947};
948
949template <class _Traits, _Trait = _Traits::__move_assignable_trait>
950class _LIBCPP_TEMPLATE_VIS __move_assignment;
951
952#define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, \
953 move_assignment) \
954 template <class... _Types> \
955 class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>, \
956 move_assignable_trait> \
957 : public __assignment<__traits<_Types...>> { \
958 using __base_type = __assignment<__traits<_Types...>>; \
959 \
960 public: \
961 using __base_type::__base_type; \
962 using __base_type::operator=; \
963 \
964 __move_assignment(const __move_assignment&) = default; \
965 __move_assignment(__move_assignment&&) = default; \
966 ~__move_assignment() = default; \
967 __move_assignment& operator=(const __move_assignment&) = default; \
968 move_assignment \
969 }
970
971_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
972 _Trait::_TriviallyAvailable,
973 __move_assignment& operator=(__move_assignment&& __that) = default;);
974
975_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
976 _Trait::_Available,
977 __move_assignment& operator=(__move_assignment&& __that) noexcept(
978 __all<(is_nothrow_move_constructible_v<_Types> &&
979 is_nothrow_move_assignable_v<_Types>)...>::value) {
980 this->__generic_assign(_VSTD::move(__that));
981 return *this;
982 });
983
984_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
985 _Trait::_Unavailable,
986 __move_assignment& operator=(__move_assignment&&) = delete;);
987
988#undef _LIBCPP_VARIANT_MOVE_ASSIGNMENT
989
990template <class _Traits, _Trait = _Traits::__copy_assignable_trait>
991class _LIBCPP_TEMPLATE_VIS __copy_assignment;
992
993#define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, \
994 copy_assignment) \
995 template <class... _Types> \
996 class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>, \
997 copy_assignable_trait> \
998 : public __move_assignment<__traits<_Types...>> { \
999 using __base_type = __move_assignment<__traits<_Types...>>; \
1000 \
1001 public: \
1002 using __base_type::__base_type; \
1003 using __base_type::operator=; \
1004 \
1005 __copy_assignment(const __copy_assignment&) = default; \
1006 __copy_assignment(__copy_assignment&&) = default; \
1007 ~__copy_assignment() = default; \
1008 copy_assignment \
1009 __copy_assignment& operator=(__copy_assignment&&) = default; \
1010 }
1011
1012_LIBCPP_VARIANT_COPY_ASSIGNMENT(
1013 _Trait::_TriviallyAvailable,
1014 __copy_assignment& operator=(const __copy_assignment& __that) = default;);
1015
1016_LIBCPP_VARIANT_COPY_ASSIGNMENT(
1017 _Trait::_Available,
1018 __copy_assignment& operator=(const __copy_assignment& __that) {
1019 this->__generic_assign(__that);
1020 return *this;
1021 });
1022
1023_LIBCPP_VARIANT_COPY_ASSIGNMENT(
1024 _Trait::_Unavailable,
1025 __copy_assignment& operator=(const __copy_assignment&) = delete;);
1026
1027#undef _LIBCPP_VARIANT_COPY_ASSIGNMENT
1028
1029template <class... _Types>
1030class _LIBCPP_TEMPLATE_VIS __impl
1031 : public __copy_assignment<__traits<_Types...>> {
1032 using __base_type = __copy_assignment<__traits<_Types...>>;
1033
1034public:
1035 using __base_type::__base_type;
1036 using __base_type::operator=;
1037
1038 template <size_t _Ip, class _Arg>
1039 inline _LIBCPP_INLINE_VISIBILITY
1040 void __assign(_Arg&& __arg) {
1041 this->__assign_alt(__access::__base::__get_alt<_Ip>(*this),
1042 _VSTD::forward<_Arg>(__arg));
1043 }
1044
1045 inline _LIBCPP_INLINE_VISIBILITY
1046 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 _VSTD::swap;
1054 swap(__this_alt.__value, __that_alt.__value);
1055 },
1056 *this,
1057 __that);
1058 } else {
1059 __impl* __lhs = this;
1060 __impl* __rhs = _VSTD::addressof(__that);
1061 if (__lhs->__move_nothrow() && !__rhs->__move_nothrow()) {
1062 _VSTD::swap(__lhs, __rhs);
1063 }
1064 __impl __tmp(_VSTD::move(*__rhs));
1065#ifndef _LIBCPP_NO_EXCEPTIONS
1066 // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
1067 // and `__tmp` is nothrow move constructible then we move `__tmp` back
1068 // into `__rhs` and provide the strong exception safety guarantee.
1069 try {
1070 this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
1071 } catch (...) {
1072 if (__tmp.__move_nothrow()) {
1073 this->__generic_construct(*__rhs, _VSTD::move(__tmp));
1074 }
1075 throw;
1076 }
1077#else
1078 this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
1079#endif
1080 this->__generic_construct(*__lhs, _VSTD::move(__tmp));
1081 }
1082 }
1083
1084private:
1085 inline _LIBCPP_INLINE_VISIBILITY
1086 bool __move_nothrow() const {
1087 constexpr bool __results[] = {is_nothrow_move_constructible_v<_Types>...};
1088 return this->valueless_by_exception() || __results[this->index()];
1089 }
1090};
1091
1092struct __no_narrowing_check {
1093 template <class _Dest, class _Source>
1094 using _Apply = __identity<_Dest>;
1095};
1096
1097struct __narrowing_check {
1098 template <class _Dest>
1099 static auto __test_impl(_Dest (&&)[1]) -> __identity<_Dest>;
1100 template <class _Dest, class _Source>
1101 using _Apply _LIBCPP_NODEBUG_TYPE = decltype(__test_impl<_Dest>({std::declval<_Source>()}));
1102};
1103
1104template <class _Dest, class _Source>
1105using __check_for_narrowing _LIBCPP_NODEBUG_TYPE =
1106 typename _If<
1107#ifdef _LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT
1108 false &&
1109#endif
1110 is_arithmetic<_Dest>::value,
1111 __narrowing_check,
1112 __no_narrowing_check
1113 >::template _Apply<_Dest, _Source>;
1114
1115template <class _Tp, size_t _Idx>
1116struct __overload {
1117 template <class _Up>
1118 auto operator()(_Tp, _Up&&) const -> __check_for_narrowing<_Tp, _Up>;
1119};
1120
1121template <class _Tp, size_t>
1122struct __overload_bool {
1123 template <class _Up, class _Ap = __uncvref_t<_Up>>
1124 auto operator()(bool, _Up&&) const
1125 -> enable_if_t<is_same_v<_Ap, bool>, __identity<_Tp>>;
1126};
1127
1128template <size_t _Idx>
1129struct __overload<bool, _Idx> : __overload_bool<bool, _Idx> {};
1130template <size_t _Idx>
1131struct __overload<bool const, _Idx> : __overload_bool<bool const, _Idx> {};
1132template <size_t _Idx>
1133struct __overload<bool volatile, _Idx> : __overload_bool<bool volatile, _Idx> {};
1134template <size_t _Idx>
1135struct __overload<bool const volatile, _Idx> : __overload_bool<bool const volatile, _Idx> {};
1136
1137template <class ..._Bases>
1138struct __all_overloads : _Bases... {
1139 void operator()() const;
1140 using _Bases::operator()...;
1141};
1142
1143template <class IdxSeq>
1144struct __make_overloads_imp;
1145
1146template <size_t ..._Idx>
1147struct __make_overloads_imp<__tuple_indices<_Idx...> > {
1148 template <class ..._Types>
1149 using _Apply _LIBCPP_NODEBUG_TYPE = __all_overloads<__overload<_Types, _Idx>...>;
1150};
1151
1152template <class ..._Types>
1153using _MakeOverloads _LIBCPP_NODEBUG_TYPE = typename __make_overloads_imp<
1154 __make_indices_imp<sizeof...(_Types), 0> >::template _Apply<_Types...>;
1155
1156template <class _Tp, class... _Types>
1157using __best_match_t =
1158 typename invoke_result_t<_MakeOverloads<_Types...>, _Tp, _Tp>::type;
1159
1160} // __variant_detail
1161
1162template <class... _Types>
1163class _LIBCPP_TEMPLATE_VIS variant
1164 : private __sfinae_ctor_base<
1165 __all<is_copy_constructible_v<_Types>...>::value,
1166 __all<is_move_constructible_v<_Types>...>::value>,
1167 private __sfinae_assign_base<
1168 __all<(is_copy_constructible_v<_Types> &&
1169 is_copy_assignable_v<_Types>)...>::value,
1170 __all<(is_move_constructible_v<_Types> &&
1171 is_move_assignable_v<_Types>)...>::value> {
1172 static_assert(0 < sizeof...(_Types),
1173 "variant must consist of at least one alternative.");
1174
1175 static_assert(__all<!is_array_v<_Types>...>::value,
1176 "variant can not have an array type as an alternative.");
1177
1178 static_assert(__all<!is_reference_v<_Types>...>::value,
1179 "variant can not have a reference type as an alternative.");
1180
1181 static_assert(__all<!is_void_v<_Types>...>::value,
1182 "variant can not have a void type as an alternative.");
1183
1184 using __first_type = variant_alternative_t<0, variant>;
1185
1186public:
1187 template <bool _Dummy = true,
1188 enable_if_t<__dependent_type<is_default_constructible<__first_type>,
1189 _Dummy>::value,
1190 int> = 0>
1191 inline _LIBCPP_INLINE_VISIBILITY
1192 constexpr variant() noexcept(is_nothrow_default_constructible_v<__first_type>)
1193 : __impl(in_place_index<0>) {}
1194
1195 variant(const variant&) = default;
1196 variant(variant&&) = default;
1197
1198 template <
1199 class _Arg,
1200 enable_if_t<!is_same_v<__uncvref_t<_Arg>, variant>, int> = 0,
1201 enable_if_t<!__is_inplace_type<__uncvref_t<_Arg>>::value, int> = 0,
1202 enable_if_t<!__is_inplace_index<__uncvref_t<_Arg>>::value, int> = 0,
1203 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1204 size_t _Ip =
1205 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1206 enable_if_t<is_constructible_v<_Tp, _Arg>, int> = 0>
1207 inline _LIBCPP_INLINE_VISIBILITY
1208 constexpr variant(_Arg&& __arg) noexcept(
1209 is_nothrow_constructible_v<_Tp, _Arg>)
1210 : __impl(in_place_index<_Ip>, _VSTD::forward<_Arg>(__arg)) {}
1211
1212 template <size_t _Ip, class... _Args,
1213 class = enable_if_t<(_Ip < sizeof...(_Types)), int>,
1214 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1215 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1216 inline _LIBCPP_INLINE_VISIBILITY
1217 explicit constexpr variant(
1218 in_place_index_t<_Ip>,
1219 _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
1220 : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
1221
1222 template <
1223 size_t _Ip,
1224 class _Up,
1225 class... _Args,
1226 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1227 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1228 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1229 int> = 0>
1230 inline _LIBCPP_INLINE_VISIBILITY
1231 explicit constexpr variant(
1232 in_place_index_t<_Ip>,
1233 initializer_list<_Up> __il,
1234 _Args&&... __args) noexcept(
1235 is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
1236 : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
1237
1238 template <
1239 class _Tp,
1240 class... _Args,
1241 size_t _Ip =
1242 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1243 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1244 inline _LIBCPP_INLINE_VISIBILITY
1245 explicit constexpr variant(in_place_type_t<_Tp>, _Args&&... __args) noexcept(
1246 is_nothrow_constructible_v<_Tp, _Args...>)
1247 : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
1248
1249 template <
1250 class _Tp,
1251 class _Up,
1252 class... _Args,
1253 size_t _Ip =
1254 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1255 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1256 int> = 0>
1257 inline _LIBCPP_INLINE_VISIBILITY
1258 explicit constexpr variant(
1259 in_place_type_t<_Tp>,
1260 initializer_list<_Up> __il,
1261 _Args&&... __args) noexcept(
1262 is_nothrow_constructible_v<_Tp, initializer_list< _Up>&, _Args...>)
1263 : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
1264
1265 ~variant() = default;
1266
1267 variant& operator=(const variant&) = default;
1268 variant& operator=(variant&&) = default;
1269
1270 template <
1271 class _Arg,
1272 enable_if_t<!is_same_v<__uncvref_t<_Arg>, variant>, int> = 0,
1273 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1274 size_t _Ip =
1275 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1276 enable_if_t<is_assignable_v<_Tp&, _Arg> && is_constructible_v<_Tp, _Arg>,
1277 int> = 0>
1278 inline _LIBCPP_INLINE_VISIBILITY
1279 variant& operator=(_Arg&& __arg) noexcept(
1280 is_nothrow_assignable_v<_Tp&, _Arg> &&
1281 is_nothrow_constructible_v<_Tp, _Arg>) {
1282 __impl.template __assign<_Ip>(_VSTD::forward<_Arg>(__arg));
1283 return *this;
1284 }
1285
1286 template <
1287 size_t _Ip,
1288 class... _Args,
1289 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1290 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1291 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1292 inline _LIBCPP_INLINE_VISIBILITY
1293 _Tp& emplace(_Args&&... __args) {
1294 return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
1295 }
1296
1297 template <
1298 size_t _Ip,
1299 class _Up,
1300 class... _Args,
1301 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1302 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1303 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1304 int> = 0>
1305 inline _LIBCPP_INLINE_VISIBILITY
1306 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1307 return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
1308 }
1309
1310 template <
1311 class _Tp,
1312 class... _Args,
1313 size_t _Ip =
1314 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1315 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1316 inline _LIBCPP_INLINE_VISIBILITY
1317 _Tp& emplace(_Args&&... __args) {
1318 return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
1319 }
1320
1321 template <
1322 class _Tp,
1323 class _Up,
1324 class... _Args,
1325 size_t _Ip =
1326 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1327 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1328 int> = 0>
1329 inline _LIBCPP_INLINE_VISIBILITY
1330 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1331 return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
1332 }
1333
1334 inline _LIBCPP_INLINE_VISIBILITY
1335 constexpr bool valueless_by_exception() const noexcept {
1336 return __impl.valueless_by_exception();
1337 }
1338
1339 inline _LIBCPP_INLINE_VISIBILITY
1340 constexpr size_t index() const noexcept { return __impl.index(); }
1341
1342 template <
1343 bool _Dummy = true,
1344 enable_if_t<
1345 __all<(
1346 __dependent_type<is_move_constructible<_Types>, _Dummy>::value &&
1347 __dependent_type<is_swappable<_Types>, _Dummy>::value)...>::value,
1348 int> = 0>
1349 inline _LIBCPP_INLINE_VISIBILITY
1350 void swap(variant& __that) noexcept(
1351 __all<(is_nothrow_move_constructible_v<_Types> &&
1352 is_nothrow_swappable_v<_Types>)...>::value) {
1353 __impl.__swap(__that.__impl);
1354 }
1355
1356private:
1357 __variant_detail::__impl<_Types...> __impl;
1358
1359 friend struct __variant_detail::__access::__variant;
1360 friend struct __variant_detail::__visitation::__variant;
1361};
1362
1363template <size_t _Ip, class... _Types>
1364inline _LIBCPP_INLINE_VISIBILITY
1365constexpr bool __holds_alternative(const variant<_Types...>& __v) noexcept {
1366 return __v.index() == _Ip;
1367}
1368
1369template <class _Tp, class... _Types>
1370inline _LIBCPP_INLINE_VISIBILITY
1371constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept {
1372 return __holds_alternative<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1373}
1374
1375template <size_t _Ip, class _Vp>
1376inline _LIBCPP_INLINE_VISIBILITY
1377_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1378constexpr auto&& __generic_get(_Vp&& __v) {
1379 using __variant_detail::__access::__variant;
1380 if (!__holds_alternative<_Ip>(__v)) {
1381 __throw_bad_variant_access();
1382 }
1383 return __variant::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v)).__value;
1384}
1385
1386template <size_t _Ip, class... _Types>
1387inline _LIBCPP_INLINE_VISIBILITY
1388_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1389constexpr variant_alternative_t<_Ip, variant<_Types...>>& get(
1390 variant<_Types...>& __v) {
1391 static_assert(_Ip < sizeof...(_Types));
1392 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1393 return __generic_get<_Ip>(__v);
1394}
1395
1396template <size_t _Ip, class... _Types>
1397inline _LIBCPP_INLINE_VISIBILITY
1398_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1399constexpr variant_alternative_t<_Ip, variant<_Types...>>&& get(
1400 variant<_Types...>&& __v) {
1401 static_assert(_Ip < sizeof...(_Types));
1402 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1403 return __generic_get<_Ip>(_VSTD::move(__v));
1404}
1405
1406template <size_t _Ip, class... _Types>
1407inline _LIBCPP_INLINE_VISIBILITY
1408_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1409constexpr const variant_alternative_t<_Ip, variant<_Types...>>& get(
1410 const variant<_Types...>& __v) {
1411 static_assert(_Ip < sizeof...(_Types));
1412 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1413 return __generic_get<_Ip>(__v);
1414}
1415
1416template <size_t _Ip, class... _Types>
1417inline _LIBCPP_INLINE_VISIBILITY
1418_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1419constexpr const variant_alternative_t<_Ip, variant<_Types...>>&& get(
1420 const variant<_Types...>&& __v) {
1421 static_assert(_Ip < sizeof...(_Types));
1422 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1423 return __generic_get<_Ip>(_VSTD::move(__v));
1424}
1425
1426template <class _Tp, class... _Types>
1427inline _LIBCPP_INLINE_VISIBILITY
1428_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1429constexpr _Tp& get(variant<_Types...>& __v) {
1430 static_assert(!is_void_v<_Tp>);
1431 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1432}
1433
1434template <class _Tp, class... _Types>
1435inline _LIBCPP_INLINE_VISIBILITY
1436_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1437constexpr _Tp&& get(variant<_Types...>&& __v) {
1438 static_assert(!is_void_v<_Tp>);
1439 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
1440 _VSTD::move(__v));
1441}
1442
1443template <class _Tp, class... _Types>
1444inline _LIBCPP_INLINE_VISIBILITY
1445_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1446constexpr const _Tp& get(const variant<_Types...>& __v) {
1447 static_assert(!is_void_v<_Tp>);
1448 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1449}
1450
1451template <class _Tp, class... _Types>
1452inline _LIBCPP_INLINE_VISIBILITY
1453_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1454constexpr const _Tp&& get(const variant<_Types...>&& __v) {
1455 static_assert(!is_void_v<_Tp>);
1456 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
1457 _VSTD::move(__v));
1458}
1459
1460template <size_t _Ip, class _Vp>
1461inline _LIBCPP_INLINE_VISIBILITY
1462constexpr auto* __generic_get_if(_Vp* __v) noexcept {
1463 using __variant_detail::__access::__variant;
1464 return __v && __holds_alternative<_Ip>(*__v)
1465 ? _VSTD::addressof(__variant::__get_alt<_Ip>(*__v).__value)
1466 : nullptr;
1467}
1468
1469template <size_t _Ip, class... _Types>
1470inline _LIBCPP_INLINE_VISIBILITY
1471constexpr add_pointer_t<variant_alternative_t<_Ip, variant<_Types...>>>
1472get_if(variant<_Types...>* __v) noexcept {
1473 static_assert(_Ip < sizeof...(_Types));
1474 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1475 return __generic_get_if<_Ip>(__v);
1476}
1477
1478template <size_t _Ip, class... _Types>
1479inline _LIBCPP_INLINE_VISIBILITY
1480constexpr add_pointer_t<const variant_alternative_t<_Ip, variant<_Types...>>>
1481get_if(const variant<_Types...>* __v) noexcept {
1482 static_assert(_Ip < sizeof...(_Types));
1483 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1484 return __generic_get_if<_Ip>(__v);
1485}
1486
1487template <class _Tp, class... _Types>
1488inline _LIBCPP_INLINE_VISIBILITY
1489constexpr add_pointer_t<_Tp>
1490get_if(variant<_Types...>* __v) noexcept {
1491 static_assert(!is_void_v<_Tp>);
1492 return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1493}
1494
1495template <class _Tp, class... _Types>
1496inline _LIBCPP_INLINE_VISIBILITY
1497constexpr add_pointer_t<const _Tp>
1498get_if(const variant<_Types...>* __v) noexcept {
1499 static_assert(!is_void_v<_Tp>);
1500 return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1501}
1502
1503template <class _Operator>
1504struct __convert_to_bool {
1505 template <class _T1, class _T2>
1506 _LIBCPP_INLINE_VISIBILITY constexpr bool operator()(_T1 && __t1, _T2&& __t2) const {
1507 static_assert(std::is_convertible<decltype(_Operator{}(_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2))), bool>::value,
1508 "the relational operator does not return a type which is implicitly convertible to bool");
1509 return _Operator{}(_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2));
1510 }
1511};
1512
1513template <class... _Types>
1514inline _LIBCPP_INLINE_VISIBILITY
1515constexpr bool operator==(const variant<_Types...>& __lhs,
1516 const variant<_Types...>& __rhs) {
1517 using __variant_detail::__visitation::__variant;
1518 if (__lhs.index() != __rhs.index()) return false;
1519 if (__lhs.valueless_by_exception()) return true;
1520 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<equal_to<>>{}, __lhs, __rhs);
1521}
1522
1523template <class... _Types>
1524inline _LIBCPP_INLINE_VISIBILITY
1525constexpr bool operator!=(const variant<_Types...>& __lhs,
1526 const variant<_Types...>& __rhs) {
1527 using __variant_detail::__visitation::__variant;
1528 if (__lhs.index() != __rhs.index()) return true;
1529 if (__lhs.valueless_by_exception()) return false;
1530 return __variant::__visit_value_at(
1531 __lhs.index(), __convert_to_bool<not_equal_to<>>{}, __lhs, __rhs);
1532}
1533
1534template <class... _Types>
1535inline _LIBCPP_INLINE_VISIBILITY
1536constexpr bool operator<(const variant<_Types...>& __lhs,
1537 const variant<_Types...>& __rhs) {
1538 using __variant_detail::__visitation::__variant;
1539 if (__rhs.valueless_by_exception()) return false;
1540 if (__lhs.valueless_by_exception()) return true;
1541 if (__lhs.index() < __rhs.index()) return true;
1542 if (__lhs.index() > __rhs.index()) return false;
1543 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<less<>>{}, __lhs, __rhs);
1544}
1545
1546template <class... _Types>
1547inline _LIBCPP_INLINE_VISIBILITY
1548constexpr bool operator>(const variant<_Types...>& __lhs,
1549 const variant<_Types...>& __rhs) {
1550 using __variant_detail::__visitation::__variant;
1551 if (__lhs.valueless_by_exception()) return false;
1552 if (__rhs.valueless_by_exception()) return true;
1553 if (__lhs.index() > __rhs.index()) return true;
1554 if (__lhs.index() < __rhs.index()) return false;
1555 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<greater<>>{}, __lhs, __rhs);
1556}
1557
1558template <class... _Types>
1559inline _LIBCPP_INLINE_VISIBILITY
1560constexpr bool operator<=(const variant<_Types...>& __lhs,
1561 const variant<_Types...>& __rhs) {
1562 using __variant_detail::__visitation::__variant;
1563 if (__lhs.valueless_by_exception()) return true;
1564 if (__rhs.valueless_by_exception()) return false;
1565 if (__lhs.index() < __rhs.index()) return true;
1566 if (__lhs.index() > __rhs.index()) return false;
1567 return __variant::__visit_value_at(
1568 __lhs.index(), __convert_to_bool<less_equal<>>{}, __lhs, __rhs);
1569}
1570
1571template <class... _Types>
1572inline _LIBCPP_INLINE_VISIBILITY
1573constexpr bool operator>=(const variant<_Types...>& __lhs,
1574 const variant<_Types...>& __rhs) {
1575 using __variant_detail::__visitation::__variant;
1576 if (__rhs.valueless_by_exception()) return true;
1577 if (__lhs.valueless_by_exception()) return false;
1578 if (__lhs.index() > __rhs.index()) return true;
1579 if (__lhs.index() < __rhs.index()) return false;
1580 return __variant::__visit_value_at(
1581 __lhs.index(), __convert_to_bool<greater_equal<>>{}, __lhs, __rhs);
1582}
1583
1584template <class _Visitor, class... _Vs>
1585inline _LIBCPP_INLINE_VISIBILITY
1586_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
1587constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
1588 using __variant_detail::__visitation::__variant;
1589 bool __results[] = {__vs.valueless_by_exception()...};
1590 for (bool __result : __results) {
1591 if (__result) {
1592 __throw_bad_variant_access();
1593 }
1594 }
1595 return __variant::__visit_value(_VSTD::forward<_Visitor>(__visitor),
1596 _VSTD::forward<_Vs>(__vs)...);
1597}
1598
1599struct _LIBCPP_TEMPLATE_VIS monostate {};
1600
1601inline _LIBCPP_INLINE_VISIBILITY
1602constexpr bool operator<(monostate, monostate) noexcept { return false; }
1603
1604inline _LIBCPP_INLINE_VISIBILITY
1605constexpr bool operator>(monostate, monostate) noexcept { return false; }
1606
1607inline _LIBCPP_INLINE_VISIBILITY
1608constexpr bool operator<=(monostate, monostate) noexcept { return true; }
1609
1610inline _LIBCPP_INLINE_VISIBILITY
1611constexpr bool operator>=(monostate, monostate) noexcept { return true; }
1612
1613inline _LIBCPP_INLINE_VISIBILITY
1614constexpr bool operator==(monostate, monostate) noexcept { return true; }
1615
1616inline _LIBCPP_INLINE_VISIBILITY
1617constexpr bool operator!=(monostate, monostate) noexcept { return false; }
1618
1619template <class... _Types>
1620inline _LIBCPP_INLINE_VISIBILITY
1621auto swap(variant<_Types...>& __lhs,
1622 variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs)))
1623 -> decltype(__lhs.swap(__rhs)) {
1624 __lhs.swap(__rhs);
1625}
1626
1627template <class... _Types>
1628struct _LIBCPP_TEMPLATE_VIS hash<
1629 __enable_hash_helper<variant<_Types...>, remove_const_t<_Types>...>> {
1630 using argument_type = variant<_Types...>;
1631 using result_type = size_t;
1632
1633 inline _LIBCPP_INLINE_VISIBILITY
1634 result_type operator()(const argument_type& __v) const {
1635 using __variant_detail::__visitation::__variant;
1636 size_t __res =
1637 __v.valueless_by_exception()
1638 ? 299792458 // Random value chosen by the universe upon creation
1639 : __variant::__visit_alt(
1640 [](const auto& __alt) {
1641 using __alt_type = __uncvref_t<decltype(__alt)>;
1642 using __value_type = remove_const_t<
1643 typename __alt_type::__value_type>;
1644 return hash<__value_type>{}(__alt.__value);
1645 },
1646 __v);
1647 return __hash_combine(__res, hash<size_t>{}(__v.index()));
1648 }
1649};
1650
1651template <>
1652struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
1653 using argument_type = monostate;
1654 using result_type = size_t;
1655
1656 inline _LIBCPP_INLINE_VISIBILITY
1657 result_type operator()(const argument_type&) const _NOEXCEPT {
1658 return 66740831; // return a fundamentally attractive random value.
1659 }
1660};
1661
1662#endif // _LIBCPP_STD_VER > 14
1663
1664_LIBCPP_END_NAMESPACE_STD
1665
1666_LIBCPP_POP_MACROS
1667
1668#endif // _LIBCPP_VARIANT
1669