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 <__availability> 201#include <__tuple> 202#include <array> 203#include <exception> 204#include <functional> 205#include <initializer_list> 206#include <new> 207#include <tuple> 208#include <type_traits> 209#include <utility> 210#include <limits> 211#include <version> 212 213#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 214#pragma GCC system_header 215#endif 216 217_LIBCPP_PUSH_MACROS 218#include <__undef_macros> 219 220namespace std { // explicitly not using versioning namespace 221 222class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS bad_variant_access : public exception { 223public: 224 virtual const char* what() const _NOEXCEPT; 225}; 226 227} // namespace std 228 229_LIBCPP_BEGIN_NAMESPACE_STD 230 231// TODO: GCC 5 lies about its support for C++17 (it says it supports it but it 232// really doesn't). That breaks variant, which uses some C++17 features. 233// Remove this once we drop support for GCC 5. 234#if _LIBCPP_STD_VER > 14 && !(defined(_LIBCPP_COMPILER_GCC) && _GNUC_VER_NEW < 6000) 235 236_LIBCPP_NORETURN 237inline _LIBCPP_INLINE_VISIBILITY 238_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 239void __throw_bad_variant_access() { 240#ifndef _LIBCPP_NO_EXCEPTIONS 241 throw bad_variant_access(); 242#else 243 _VSTD::abort(); 244#endif 245} 246 247template <class... _Types> 248class _LIBCPP_TEMPLATE_VIS variant; 249 250template <class _Tp> 251struct _LIBCPP_TEMPLATE_VIS variant_size; 252 253template <class _Tp> 254_LIBCPP_INLINE_VAR constexpr size_t variant_size_v = variant_size<_Tp>::value; 255 256template <class _Tp> 257struct _LIBCPP_TEMPLATE_VIS variant_size<const _Tp> : variant_size<_Tp> {}; 258 259template <class _Tp> 260struct _LIBCPP_TEMPLATE_VIS variant_size<volatile _Tp> : variant_size<_Tp> {}; 261 262template <class _Tp> 263struct _LIBCPP_TEMPLATE_VIS variant_size<const volatile _Tp> 264 : variant_size<_Tp> {}; 265 266template <class... _Types> 267struct _LIBCPP_TEMPLATE_VIS variant_size<variant<_Types...>> 268 : integral_constant<size_t, sizeof...(_Types)> {}; 269 270template <size_t _Ip, class _Tp> 271struct _LIBCPP_TEMPLATE_VIS variant_alternative; 272 273template <size_t _Ip, class _Tp> 274using variant_alternative_t = typename variant_alternative<_Ip, _Tp>::type; 275 276template <size_t _Ip, class _Tp> 277struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const _Tp> 278 : add_const<variant_alternative_t<_Ip, _Tp>> {}; 279 280template <size_t _Ip, class _Tp> 281struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, volatile _Tp> 282 : add_volatile<variant_alternative_t<_Ip, _Tp>> {}; 283 284template <size_t _Ip, class _Tp> 285struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const volatile _Tp> 286 : add_cv<variant_alternative_t<_Ip, _Tp>> {}; 287 288template <size_t _Ip, class... _Types> 289struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, variant<_Types...>> { 290 static_assert(_Ip < sizeof...(_Types), "Index out of bounds in std::variant_alternative<>"); 291 using type = __type_pack_element<_Ip, _Types...>; 292}; 293 294_LIBCPP_INLINE_VAR constexpr size_t variant_npos = static_cast<size_t>(-1); 295 296constexpr int __choose_index_type(unsigned int __num_elem) { 297 if (__num_elem < std::numeric_limits<unsigned char>::max()) 298 return 0; 299 if (__num_elem < std::numeric_limits<unsigned short>::max()) 300 return 1; 301 return 2; 302} 303 304template <size_t _NumAlts> 305using __variant_index_t = 306#ifndef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION 307 unsigned int; 308#else 309 std::tuple_element_t< 310 __choose_index_type(_NumAlts), 311 std::tuple<unsigned char, unsigned short, unsigned int> 312 >; 313#endif 314 315template <class _IndexType> 316constexpr _IndexType __variant_npos = static_cast<_IndexType>(-1); 317 318namespace __find_detail { 319 320template <class _Tp, class... _Types> 321inline _LIBCPP_INLINE_VISIBILITY 322constexpr size_t __find_index() { 323 constexpr bool __matches[] = {is_same_v<_Tp, _Types>...}; 324 size_t __result = __not_found; 325 for (size_t __i = 0; __i < sizeof...(_Types); ++__i) { 326 if (__matches[__i]) { 327 if (__result != __not_found) { 328 return __ambiguous; 329 } 330 __result = __i; 331 } 332 } 333 return __result; 334} 335 336template <size_t _Index> 337struct __find_unambiguous_index_sfinae_impl 338 : integral_constant<size_t, _Index> {}; 339 340template <> 341struct __find_unambiguous_index_sfinae_impl<__not_found> {}; 342 343template <> 344struct __find_unambiguous_index_sfinae_impl<__ambiguous> {}; 345 346template <class _Tp, class... _Types> 347struct __find_unambiguous_index_sfinae 348 : __find_unambiguous_index_sfinae_impl<__find_index<_Tp, _Types...>()> {}; 349 350} // namespace __find_detail 351 352namespace __variant_detail { 353 354struct __valueless_t {}; 355 356enum class _Trait { _TriviallyAvailable, _Available, _Unavailable }; 357 358template <class _Tp, 359 template <class> class _IsTriviallyAvailable, 360 template <class> class _IsAvailable> 361constexpr _Trait __trait = 362 _IsTriviallyAvailable<_Tp>::value 363 ? _Trait::_TriviallyAvailable 364 : _IsAvailable<_Tp>::value ? _Trait::_Available : _Trait::_Unavailable; 365 366inline _LIBCPP_INLINE_VISIBILITY 367constexpr _Trait __common_trait(initializer_list<_Trait> __traits) { 368 _Trait __result = _Trait::_TriviallyAvailable; 369 for (_Trait __t : __traits) { 370 if (static_cast<int>(__t) > static_cast<int>(__result)) { 371 __result = __t; 372 } 373 } 374 return __result; 375} 376 377template <class... _Types> 378struct __traits { 379 static constexpr _Trait __copy_constructible_trait = 380 __common_trait({__trait<_Types, 381 is_trivially_copy_constructible, 382 is_copy_constructible>...}); 383 384 static constexpr _Trait __move_constructible_trait = 385 __common_trait({__trait<_Types, 386 is_trivially_move_constructible, 387 is_move_constructible>...}); 388 389 static constexpr _Trait __copy_assignable_trait = __common_trait( 390 {__copy_constructible_trait, 391 __trait<_Types, is_trivially_copy_assignable, is_copy_assignable>...}); 392 393 static constexpr _Trait __move_assignable_trait = __common_trait( 394 {__move_constructible_trait, 395 __trait<_Types, is_trivially_move_assignable, is_move_assignable>...}); 396 397 static constexpr _Trait __destructible_trait = __common_trait( 398 {__trait<_Types, is_trivially_destructible, is_destructible>...}); 399}; 400 401namespace __access { 402 403struct __union { 404 template <class _Vp> 405 inline _LIBCPP_INLINE_VISIBILITY 406 static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<0>) { 407 return _VSTD::forward<_Vp>(__v).__head; 408 } 409 410 template <class _Vp, size_t _Ip> 411 inline _LIBCPP_INLINE_VISIBILITY 412 static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<_Ip>) { 413 return __get_alt(_VSTD::forward<_Vp>(__v).__tail, in_place_index<_Ip - 1>); 414 } 415}; 416 417struct __base { 418 template <size_t _Ip, class _Vp> 419 inline _LIBCPP_INLINE_VISIBILITY 420 static constexpr auto&& __get_alt(_Vp&& __v) { 421 return __union::__get_alt(_VSTD::forward<_Vp>(__v).__data, 422 in_place_index<_Ip>); 423 } 424}; 425 426struct __variant { 427 template <size_t _Ip, class _Vp> 428 inline _LIBCPP_INLINE_VISIBILITY 429 static constexpr auto&& __get_alt(_Vp&& __v) { 430 return __base::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v).__impl); 431 } 432}; 433 434} // namespace __access 435 436namespace __visitation { 437 438#define _LIBCPP_VARIANT_CASES_4(_Case, _Base) \ 439 _Case(_Base + 0) \ 440 _Case(_Base + 1) \ 441 _Case(_Base + 2) \ 442 _Case(_Base + 3) 443 444#define _LIBCPP_VARIANT_CASES_16(_Case, _Base) \ 445 _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 0) \ 446 _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 1) \ 447 _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 2) \ 448 _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 3) 449 450#define _LIBCPP_VARIANT_CASES_64(_Case, _Base) \ 451 _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 0) \ 452 _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 1) \ 453 _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 2) \ 454 _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 3) 455 456#define _LIBCPP_VARIANT_CASES_256(_Case, _Base) \ 457 _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 0) \ 458 _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 1) \ 459 _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 2) \ 460 _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 3) 461 462#define _LIBCPP_VARIANT_CASES(_NumCases, _Case) \ 463 _LIBCPP_CONCAT(_LIBCPP_VARIANT_CASES_, _NumCases)(_Case, 0) 464 465#define _LIBCPP_VARIANT_SWITCH_MAX 256 466 467template <class _Iter, class _Fp, size_t... _Is> 468inline _LIBCPP_INLINE_VISIBILITY 469static constexpr void __fill_cartesian_impl( 470 _Iter __iter, _Fp __f, index_sequence<_Is...>) { 471 *__iter = __f(integral_constant<size_t, _Is>{}...); 472} 473 474template <class _Iter, class _Fp, size_t... _Is, size_t... _Js, class... _Ls> 475inline _LIBCPP_INLINE_VISIBILITY 476static constexpr void __fill_cartesian_impl( 477 _Iter __iter, _Fp __f, index_sequence<_Is...>, index_sequence<_Js...>, _Ls... __ls) { 478 constexpr size_t _Mp = (1 * ... * _Ls::size()); 479 (__fill_cartesian_impl( 480 __iter + _Js * _Mp, __f, index_sequence<_Is..., _Js>{}, __ls...), ...); 481} 482 483template <size_t... _Ns, class _Iter, class _Fp> 484inline _LIBCPP_INLINE_VISIBILITY 485static constexpr void __fill_cartesian(_Iter __iter, _Fp __f) { 486 __fill_cartesian_impl( 487 __iter, __f, index_sequence<>{}, make_index_sequence<_Ns>{}...); 488} 489 490template <size_t _Np, size_t... _Ns> 491struct __multi { 492 inline _LIBCPP_INLINE_VISIBILITY 493 static constexpr size_t __size = (_Np * ... * _Ns); 494 495 inline _LIBCPP_INLINE_VISIBILITY 496 static constexpr size_t 497 __index(const size_t (&__is)[sizeof...(_Ns) + 1]) noexcept { 498 constexpr size_t __ns[] = {_Ns..., 1}; 499 size_t __result = 0; 500 for (size_t __i = 0; __i < sizeof...(_Ns) + 1; ++__i) { 501 if (__is[__i] == variant_npos) { 502 return variant_npos; 503 } 504 __result += __is[__i]; 505 __result *= __ns[__i]; 506 } 507 return __result; 508 } 509}; 510 511template <size_t... _Ns> 512struct __indices { 513 inline _LIBCPP_INLINE_VISIBILITY 514 static constexpr auto __value = [] { 515 using _Tp = array<size_t, sizeof...(_Ns)>; 516 array<_Tp, (1 * ... * _Ns)> __result = {}; 517 __fill_cartesian<_Ns...>(__result.begin(), 518 [](auto... __is) -> _Tp { return {__is...}; }); 519 return __result; 520 }(); 521}; 522 523template <size_t... _Ns, class _Fp, class _Rp, class... _Args> 524inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 525static constexpr auto __make_vtable_impl(_Fp __f, _Rp (*)(_Args...)) { 526 array<_Rp (*)(_Args...), (1 * ... * _Ns) + 1> __result = { 527 [](_Args...) -> _Rp { __throw_bad_variant_access(); } 528 }; 529 __fill_cartesian<_Ns...>(__result.begin() + 1, __f); 530 return __result; 531} 532 533template <size_t... _Ns, class _Fp> 534inline _LIBCPP_INLINE_VISIBILITY 535static constexpr auto __make_vtable(_Fp __f) { 536 using _Tp = decltype(__f(integral_constant<size_t, (_Ns, 0)>{}...)); 537 return __make_vtable_impl<_Ns...>(__f, _Tp{}); 538} 539 540struct __base { 541 template <class _Vis, class... _Vs> 542 struct __dispatch { 543 template <size_t... _Is> 544 inline _LIBCPP_INLINE_VISIBILITY 545 constexpr auto operator()(integral_constant<size_t, _Is>...) const noexcept { 546 return +[](_Vis&& __vis, _Vs&&... __vs) -> decltype(auto) { 547 return __invoke_constexpr( 548 _VSTD::forward<_Vis>(__vis), 549 __access::__base::__get_alt<_Is>(_VSTD::forward<_Vs>(__vs))...); 550 }; 551 } 552 }; 553 554 template <class _Vis, class _Vp, class _Wp> 555 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 556 static constexpr decltype(auto) 557 __visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) { 558 constexpr size_t __size = __uncvref_t<_Vp>::__size(); 559 static_assert(__size == __uncvref_t<_Wp>::__size()); 560 constexpr auto __dispatch_at = [](auto __i) { 561 return __dispatch<_Vis, _Vp, _Wp>{}(__i, __i); 562 }; 563#define _LIBCPP_VARIANT_CASE(_Ip) \ 564 case _Ip: { \ 565 if constexpr (_Ip < __size) { \ 566 return __dispatch_at(integral_constant<size_t, _Ip>{})( \ 567 _VSTD::forward<_Vis>(__vis), \ 568 _VSTD::forward<_Vp>(__v), \ 569 _VSTD::forward<_Wp>(__w)); \ 570 } else { \ 571 _LIBCPP_UNREACHABLE(); \ 572 } \ 573 } 574 if constexpr (__size <= _LIBCPP_VARIANT_SWITCH_MAX) { 575 switch (__index) { 576 _LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE) 577 default: __throw_bad_variant_access(); 578 } 579 } else { 580 constexpr auto __vtable = __make_vtable<__size>(__dispatch_at); 581 return __vtable[__index + 1](_VSTD::forward<_Vis>(__vis), 582 _VSTD::forward<_Vp>(__v), 583 _VSTD::forward<_Wp>(__w)); 584 } 585#undef _LIBCPP_VARIANT_CASE 586 } 587 588 template <size_t... _Is, class _Vis, class... _Vs> 589 inline _LIBCPP_INLINE_VISIBILITY 590 static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) { 591 if constexpr (sizeof...(_Vs) == 0) { 592 return __invoke_constexpr(_VSTD::forward<_Vis>(__vis)); 593 } else { 594 return __visit_alt_impl(index_sequence_for<_Vs...>{}, 595 _VSTD::forward<_Vis>(__vis), 596 _VSTD::forward<_Vs>(__vs)...); 597 } 598 } 599 600 template <size_t... _Is, class _Vis, class... _Vs> 601 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 602 static constexpr decltype(auto) 603 __visit_alt_impl(index_sequence<_Is...>, _Vis&& __vis, _Vs&&... __vs) { 604 using __multi = __multi<__uncvref_t<_Vs>::__size()...>; 605 constexpr __dispatch<_Vis, _Vs...> __dispatch; 606#define _LIBCPP_VARIANT_CASE(_Ip) \ 607 case _Ip: { \ 608 if constexpr (_Ip < __multi::__size) { \ 609 return __dispatch(integral_constant<size_t, __itable[_Ip][_Is]>{}...)( \ 610 _VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...); \ 611 } else { \ 612 _LIBCPP_UNREACHABLE(); \ 613 } \ 614 } 615 if constexpr (__multi::__size <= _LIBCPP_VARIANT_SWITCH_MAX) { 616 constexpr const auto& __itable = 617 __indices<__uncvref_t<_Vs>::__size()...>::__value; 618 switch (__multi::__index({__vs.index()...})) { 619 _LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE) 620 default: __throw_bad_variant_access(); 621 } 622 } else { 623 constexpr auto __vtable = 624 __make_vtable<__uncvref_t<_Vs>::__size()...>(__dispatch); 625 return __vtable[__multi::__index({__vs.index()...}) + 1]( 626 _VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...); 627 } 628#undef _LIBCPP_VARIANT_CASE 629 } 630}; 631 632struct __variant { 633 template <class _Vis, class _Vp, class _Wp> 634 inline _LIBCPP_INLINE_VISIBILITY 635 static constexpr decltype(auto) 636 __visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) { 637 return __base::__visit_alt_at(__index, 638 _VSTD::forward<_Vis>(__vis), 639 _VSTD::forward<_Vp>(__v).__impl, 640 _VSTD::forward<_Wp>(__w).__impl); 641 } 642 643 template <class _Vis, class... _Vs> 644 inline _LIBCPP_INLINE_VISIBILITY 645 static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) { 646 return __base::__visit_alt(_VSTD::forward<_Vis>(__vis), 647 _VSTD::forward<_Vs>(__vs).__impl...); 648 } 649 650 template <class _Vis, class _Vp, class _Wp> 651 inline _LIBCPP_INLINE_VISIBILITY 652 static constexpr decltype(auto) 653 __visit_value_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) { 654 return __visit_alt_at(__index, 655 __make_value_visitor(_VSTD::forward<_Vis>(__vis)), 656 _VSTD::forward<_Vp>(__v), 657 _VSTD::forward<_Wp>(__w)); 658 } 659 660 template <class _Vis, class... _Vs> 661 inline _LIBCPP_INLINE_VISIBILITY 662 static constexpr decltype(auto) __visit_value(_Vis&& __vis, _Vs&&... __vs) { 663 return __visit_alt(__make_value_visitor(_VSTD::forward<_Vis>(__vis)), 664 _VSTD::forward<_Vs>(__vs)...); 665 } 666 667private: 668 template <class _Vis, class... _Values> 669 inline _LIBCPP_INLINE_VISIBILITY 670 static constexpr void __std_visit_exhaustive_visitor_check() { 671 static_assert(is_invocable_v<_Vis, _Values...>, 672 "`std::visit` requires the visitor to be exhaustive."); 673 } 674 675 template <class _Vis> 676 struct __value_visitor { 677 template <class... _Alts> 678 inline _LIBCPP_INLINE_VISIBILITY 679 constexpr decltype(auto) operator()(_Alts&&... __alts) const { 680 __std_visit_exhaustive_visitor_check< 681 _Vis, decltype((_VSTD::forward<_Alts>(__alts).__value))...>(); 682 return __invoke_constexpr(_VSTD::forward<_Vis>(__vis), 683 _VSTD::forward<_Alts>(__alts).__value...); 684 } 685 _Vis&& __vis; 686 }; 687 688 template <class _Vis> 689 inline _LIBCPP_INLINE_VISIBILITY 690 static constexpr auto __make_value_visitor(_Vis&& __vis) { 691 return __value_visitor<_Vis>{_VSTD::forward<_Vis>(__vis)}; 692 } 693}; 694 695#undef _LIBCPP_VARIANT_SWITCH_MAX 696#undef _LIBCPP_VARIANT_CASES 697#undef _LIBCPP_VARIANT_CASES_256 698#undef _LIBCPP_VARIANT_CASES_64 699#undef _LIBCPP_VARIANT_CASES_16 700#undef _LIBCPP_VARIANT_CASES_4 701 702} // namespace __visitation 703 704template <size_t _Index, class _Tp> 705struct _LIBCPP_TEMPLATE_VIS __alt { 706 using __value_type = _Tp; 707 708 template <class... _Args> 709 inline _LIBCPP_INLINE_VISIBILITY 710 explicit constexpr __alt(in_place_t, _Args&&... __args) 711 : __value(_VSTD::forward<_Args>(__args)...) {} 712 713 __value_type __value; 714}; 715 716template <_Trait _DestructibleTrait, size_t _Index, class... _Types> 717union _LIBCPP_TEMPLATE_VIS __union; 718 719template <_Trait _DestructibleTrait, size_t _Index> 720union _LIBCPP_TEMPLATE_VIS __union<_DestructibleTrait, _Index> {}; 721 722#define _LIBCPP_VARIANT_UNION(destructible_trait, destructor) \ 723 template <size_t _Index, class _Tp, class... _Types> \ 724 union _LIBCPP_TEMPLATE_VIS __union<destructible_trait, \ 725 _Index, \ 726 _Tp, \ 727 _Types...> { \ 728 public: \ 729 inline _LIBCPP_INLINE_VISIBILITY \ 730 explicit constexpr __union(__valueless_t) noexcept : __dummy{} {} \ 731 \ 732 template <class... _Args> \ 733 inline _LIBCPP_INLINE_VISIBILITY \ 734 explicit constexpr __union(in_place_index_t<0>, _Args&&... __args) \ 735 : __head(in_place, _VSTD::forward<_Args>(__args)...) {} \ 736 \ 737 template <size_t _Ip, class... _Args> \ 738 inline _LIBCPP_INLINE_VISIBILITY \ 739 explicit constexpr __union(in_place_index_t<_Ip>, _Args&&... __args) \ 740 : __tail(in_place_index<_Ip - 1>, _VSTD::forward<_Args>(__args)...) {} \ 741 \ 742 __union(const __union&) = default; \ 743 __union(__union&&) = default; \ 744 \ 745 destructor \ 746 \ 747 __union& operator=(const __union&) = default; \ 748 __union& operator=(__union&&) = default; \ 749 \ 750 private: \ 751 char __dummy; \ 752 __alt<_Index, _Tp> __head; \ 753 __union<destructible_trait, _Index + 1, _Types...> __tail; \ 754 \ 755 friend struct __access::__union; \ 756 } 757 758_LIBCPP_VARIANT_UNION(_Trait::_TriviallyAvailable, ~__union() = default;); 759_LIBCPP_VARIANT_UNION(_Trait::_Available, ~__union() {}); 760_LIBCPP_VARIANT_UNION(_Trait::_Unavailable, ~__union() = delete;); 761 762#undef _LIBCPP_VARIANT_UNION 763 764template <_Trait _DestructibleTrait, class... _Types> 765class _LIBCPP_TEMPLATE_VIS __base { 766public: 767 using __index_t = __variant_index_t<sizeof...(_Types)>; 768 769 inline _LIBCPP_INLINE_VISIBILITY 770 explicit constexpr __base(__valueless_t tag) noexcept 771 : __data(tag), __index(__variant_npos<__index_t>) {} 772 773 template <size_t _Ip, class... _Args> 774 inline _LIBCPP_INLINE_VISIBILITY 775 explicit constexpr __base(in_place_index_t<_Ip>, _Args&&... __args) 776 : 777 __data(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...), 778 __index(_Ip) {} 779 780 inline _LIBCPP_INLINE_VISIBILITY 781 constexpr bool valueless_by_exception() const noexcept { 782 return index() == variant_npos; 783 } 784 785 inline _LIBCPP_INLINE_VISIBILITY 786 constexpr size_t index() const noexcept { 787 return __index == __variant_npos<__index_t> ? variant_npos : __index; 788 } 789 790protected: 791 inline _LIBCPP_INLINE_VISIBILITY 792 constexpr auto&& __as_base() & { return *this; } 793 794 inline _LIBCPP_INLINE_VISIBILITY 795 constexpr auto&& __as_base() && { return _VSTD::move(*this); } 796 797 inline _LIBCPP_INLINE_VISIBILITY 798 constexpr auto&& __as_base() const & { return *this; } 799 800 inline _LIBCPP_INLINE_VISIBILITY 801 constexpr auto&& __as_base() const && { return _VSTD::move(*this); } 802 803 inline _LIBCPP_INLINE_VISIBILITY 804 static constexpr size_t __size() { return sizeof...(_Types); } 805 806 __union<_DestructibleTrait, 0, _Types...> __data; 807 __index_t __index; 808 809 friend struct __access::__base; 810 friend struct __visitation::__base; 811}; 812 813template <class _Traits, _Trait = _Traits::__destructible_trait> 814class _LIBCPP_TEMPLATE_VIS __dtor; 815 816#define _LIBCPP_VARIANT_DESTRUCTOR(destructible_trait, destructor, destroy) \ 817 template <class... _Types> \ 818 class _LIBCPP_TEMPLATE_VIS __dtor<__traits<_Types...>, \ 819 destructible_trait> \ 820 : public __base<destructible_trait, _Types...> { \ 821 using __base_type = __base<destructible_trait, _Types...>; \ 822 using __index_t = typename __base_type::__index_t; \ 823 \ 824 public: \ 825 using __base_type::__base_type; \ 826 using __base_type::operator=; \ 827 \ 828 __dtor(const __dtor&) = default; \ 829 __dtor(__dtor&&) = default; \ 830 destructor \ 831 __dtor& operator=(const __dtor&) = default; \ 832 __dtor& operator=(__dtor&&) = default; \ 833 \ 834 protected: \ 835 inline _LIBCPP_INLINE_VISIBILITY \ 836 destroy \ 837 } 838 839_LIBCPP_VARIANT_DESTRUCTOR( 840 _Trait::_TriviallyAvailable, 841 ~__dtor() = default;, 842 void __destroy() noexcept { this->__index = __variant_npos<__index_t>; }); 843 844_LIBCPP_VARIANT_DESTRUCTOR( 845 _Trait::_Available, 846 ~__dtor() { __destroy(); }, 847 void __destroy() noexcept { 848 if (!this->valueless_by_exception()) { 849 __visitation::__base::__visit_alt( 850 [](auto& __alt) noexcept { 851 using __alt_type = __uncvref_t<decltype(__alt)>; 852 __alt.~__alt_type(); 853 }, 854 *this); 855 } 856 this->__index = __variant_npos<__index_t>; 857 }); 858 859_LIBCPP_VARIANT_DESTRUCTOR( 860 _Trait::_Unavailable, 861 ~__dtor() = delete;, 862 void __destroy() noexcept = delete;); 863 864#undef _LIBCPP_VARIANT_DESTRUCTOR 865 866template <class _Traits> 867class _LIBCPP_TEMPLATE_VIS __ctor : public __dtor<_Traits> { 868 using __base_type = __dtor<_Traits>; 869 870public: 871 using __base_type::__base_type; 872 using __base_type::operator=; 873 874protected: 875 template <size_t _Ip, class _Tp, class... _Args> 876 inline _LIBCPP_INLINE_VISIBILITY 877 static _Tp& __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) { 878 auto* __result = ::new ((void*)_VSTD::addressof(__a)) 879 __alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...); 880 return __result->__value; 881 } 882 883 template <class _Rhs> 884 inline _LIBCPP_INLINE_VISIBILITY 885 static void __generic_construct(__ctor& __lhs, _Rhs&& __rhs) { 886 __lhs.__destroy(); 887 if (!__rhs.valueless_by_exception()) { 888 __visitation::__base::__visit_alt_at( 889 __rhs.index(), 890 [](auto& __lhs_alt, auto&& __rhs_alt) { 891 __construct_alt( 892 __lhs_alt, 893 _VSTD::forward<decltype(__rhs_alt)>(__rhs_alt).__value); 894 }, 895 __lhs, _VSTD::forward<_Rhs>(__rhs)); 896 __lhs.__index = __rhs.index(); 897 } 898 } 899}; 900 901template <class _Traits, _Trait = _Traits::__move_constructible_trait> 902class _LIBCPP_TEMPLATE_VIS __move_constructor; 903 904#define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, \ 905 move_constructor) \ 906 template <class... _Types> \ 907 class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \ 908 move_constructible_trait> \ 909 : public __ctor<__traits<_Types...>> { \ 910 using __base_type = __ctor<__traits<_Types...>>; \ 911 \ 912 public: \ 913 using __base_type::__base_type; \ 914 using __base_type::operator=; \ 915 \ 916 __move_constructor(const __move_constructor&) = default; \ 917 move_constructor \ 918 ~__move_constructor() = default; \ 919 __move_constructor& operator=(const __move_constructor&) = default; \ 920 __move_constructor& operator=(__move_constructor&&) = default; \ 921 } 922 923_LIBCPP_VARIANT_MOVE_CONSTRUCTOR( 924 _Trait::_TriviallyAvailable, 925 __move_constructor(__move_constructor&& __that) = default;); 926 927_LIBCPP_VARIANT_MOVE_CONSTRUCTOR( 928 _Trait::_Available, 929 __move_constructor(__move_constructor&& __that) noexcept( 930 __all<is_nothrow_move_constructible_v<_Types>...>::value) 931 : __move_constructor(__valueless_t{}) { 932 this->__generic_construct(*this, _VSTD::move(__that)); 933 }); 934 935_LIBCPP_VARIANT_MOVE_CONSTRUCTOR( 936 _Trait::_Unavailable, 937 __move_constructor(__move_constructor&&) = delete;); 938 939#undef _LIBCPP_VARIANT_MOVE_CONSTRUCTOR 940 941template <class _Traits, _Trait = _Traits::__copy_constructible_trait> 942class _LIBCPP_TEMPLATE_VIS __copy_constructor; 943 944#define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, \ 945 copy_constructor) \ 946 template <class... _Types> \ 947 class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>, \ 948 copy_constructible_trait> \ 949 : public __move_constructor<__traits<_Types...>> { \ 950 using __base_type = __move_constructor<__traits<_Types...>>; \ 951 \ 952 public: \ 953 using __base_type::__base_type; \ 954 using __base_type::operator=; \ 955 \ 956 copy_constructor \ 957 __copy_constructor(__copy_constructor&&) = default; \ 958 ~__copy_constructor() = default; \ 959 __copy_constructor& operator=(const __copy_constructor&) = default; \ 960 __copy_constructor& operator=(__copy_constructor&&) = default; \ 961 } 962 963_LIBCPP_VARIANT_COPY_CONSTRUCTOR( 964 _Trait::_TriviallyAvailable, 965 __copy_constructor(const __copy_constructor& __that) = default;); 966 967_LIBCPP_VARIANT_COPY_CONSTRUCTOR( 968 _Trait::_Available, 969 __copy_constructor(const __copy_constructor& __that) 970 : __copy_constructor(__valueless_t{}) { 971 this->__generic_construct(*this, __that); 972 }); 973 974_LIBCPP_VARIANT_COPY_CONSTRUCTOR( 975 _Trait::_Unavailable, 976 __copy_constructor(const __copy_constructor&) = delete;); 977 978#undef _LIBCPP_VARIANT_COPY_CONSTRUCTOR 979 980template <class _Traits> 981class _LIBCPP_TEMPLATE_VIS __assignment : public __copy_constructor<_Traits> { 982 using __base_type = __copy_constructor<_Traits>; 983 984public: 985 using __base_type::__base_type; 986 using __base_type::operator=; 987 988 template <size_t _Ip, class... _Args> 989 inline _LIBCPP_INLINE_VISIBILITY 990 auto& __emplace(_Args&&... __args) { 991 this->__destroy(); 992 auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this), 993 _VSTD::forward<_Args>(__args)...); 994 this->__index = _Ip; 995 return __res; 996 } 997 998protected: 999 template <size_t _Ip, class _Tp, class _Arg> 1000 inline _LIBCPP_INLINE_VISIBILITY 1001 void __assign_alt(__alt<_Ip, _Tp>& __a, _Arg&& __arg) { 1002 if (this->index() == _Ip) { 1003 __a.__value = _VSTD::forward<_Arg>(__arg); 1004 } else { 1005 struct { 1006 void operator()(true_type) const { 1007 __this->__emplace<_Ip>(_VSTD::forward<_Arg>(__arg)); 1008 } 1009 void operator()(false_type) const { 1010 __this->__emplace<_Ip>(_Tp(_VSTD::forward<_Arg>(__arg))); 1011 } 1012 __assignment* __this; 1013 _Arg&& __arg; 1014 } __impl{this, _VSTD::forward<_Arg>(__arg)}; 1015 __impl(bool_constant<is_nothrow_constructible_v<_Tp, _Arg> || 1016 !is_nothrow_move_constructible_v<_Tp>>{}); 1017 } 1018 } 1019 1020 template <class _That> 1021 inline _LIBCPP_INLINE_VISIBILITY 1022 void __generic_assign(_That&& __that) { 1023 if (this->valueless_by_exception() && __that.valueless_by_exception()) { 1024 // do nothing. 1025 } else if (__that.valueless_by_exception()) { 1026 this->__destroy(); 1027 } else { 1028 __visitation::__base::__visit_alt_at( 1029 __that.index(), 1030 [this](auto& __this_alt, auto&& __that_alt) { 1031 this->__assign_alt( 1032 __this_alt, 1033 _VSTD::forward<decltype(__that_alt)>(__that_alt).__value); 1034 }, 1035 *this, _VSTD::forward<_That>(__that)); 1036 } 1037 } 1038}; 1039 1040template <class _Traits, _Trait = _Traits::__move_assignable_trait> 1041class _LIBCPP_TEMPLATE_VIS __move_assignment; 1042 1043#define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, \ 1044 move_assignment) \ 1045 template <class... _Types> \ 1046 class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>, \ 1047 move_assignable_trait> \ 1048 : public __assignment<__traits<_Types...>> { \ 1049 using __base_type = __assignment<__traits<_Types...>>; \ 1050 \ 1051 public: \ 1052 using __base_type::__base_type; \ 1053 using __base_type::operator=; \ 1054 \ 1055 __move_assignment(const __move_assignment&) = default; \ 1056 __move_assignment(__move_assignment&&) = default; \ 1057 ~__move_assignment() = default; \ 1058 __move_assignment& operator=(const __move_assignment&) = default; \ 1059 move_assignment \ 1060 } 1061 1062_LIBCPP_VARIANT_MOVE_ASSIGNMENT( 1063 _Trait::_TriviallyAvailable, 1064 __move_assignment& operator=(__move_assignment&& __that) = default;); 1065 1066_LIBCPP_VARIANT_MOVE_ASSIGNMENT( 1067 _Trait::_Available, 1068 __move_assignment& operator=(__move_assignment&& __that) noexcept( 1069 __all<(is_nothrow_move_constructible_v<_Types> && 1070 is_nothrow_move_assignable_v<_Types>)...>::value) { 1071 this->__generic_assign(_VSTD::move(__that)); 1072 return *this; 1073 }); 1074 1075_LIBCPP_VARIANT_MOVE_ASSIGNMENT( 1076 _Trait::_Unavailable, 1077 __move_assignment& operator=(__move_assignment&&) = delete;); 1078 1079#undef _LIBCPP_VARIANT_MOVE_ASSIGNMENT 1080 1081template <class _Traits, _Trait = _Traits::__copy_assignable_trait> 1082class _LIBCPP_TEMPLATE_VIS __copy_assignment; 1083 1084#define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, \ 1085 copy_assignment) \ 1086 template <class... _Types> \ 1087 class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>, \ 1088 copy_assignable_trait> \ 1089 : public __move_assignment<__traits<_Types...>> { \ 1090 using __base_type = __move_assignment<__traits<_Types...>>; \ 1091 \ 1092 public: \ 1093 using __base_type::__base_type; \ 1094 using __base_type::operator=; \ 1095 \ 1096 __copy_assignment(const __copy_assignment&) = default; \ 1097 __copy_assignment(__copy_assignment&&) = default; \ 1098 ~__copy_assignment() = default; \ 1099 copy_assignment \ 1100 __copy_assignment& operator=(__copy_assignment&&) = default; \ 1101 } 1102 1103_LIBCPP_VARIANT_COPY_ASSIGNMENT( 1104 _Trait::_TriviallyAvailable, 1105 __copy_assignment& operator=(const __copy_assignment& __that) = default;); 1106 1107_LIBCPP_VARIANT_COPY_ASSIGNMENT( 1108 _Trait::_Available, 1109 __copy_assignment& operator=(const __copy_assignment& __that) { 1110 this->__generic_assign(__that); 1111 return *this; 1112 }); 1113 1114_LIBCPP_VARIANT_COPY_ASSIGNMENT( 1115 _Trait::_Unavailable, 1116 __copy_assignment& operator=(const __copy_assignment&) = delete;); 1117 1118#undef _LIBCPP_VARIANT_COPY_ASSIGNMENT 1119 1120template <class... _Types> 1121class _LIBCPP_TEMPLATE_VIS __impl 1122 : public __copy_assignment<__traits<_Types...>> { 1123 using __base_type = __copy_assignment<__traits<_Types...>>; 1124 1125public: 1126 using __base_type::__base_type; 1127 using __base_type::operator=; 1128 1129 template <size_t _Ip, class _Arg> 1130 inline _LIBCPP_INLINE_VISIBILITY 1131 void __assign(_Arg&& __arg) { 1132 this->__assign_alt(__access::__base::__get_alt<_Ip>(*this), 1133 _VSTD::forward<_Arg>(__arg)); 1134 } 1135 1136 inline _LIBCPP_INLINE_VISIBILITY 1137 void __swap(__impl& __that) { 1138 if (this->valueless_by_exception() && __that.valueless_by_exception()) { 1139 // do nothing. 1140 } else if (this->index() == __that.index()) { 1141 __visitation::__base::__visit_alt_at( 1142 this->index(), 1143 [](auto& __this_alt, auto& __that_alt) { 1144 using _VSTD::swap; 1145 swap(__this_alt.__value, __that_alt.__value); 1146 }, 1147 *this, 1148 __that); 1149 } else { 1150 __impl* __lhs = this; 1151 __impl* __rhs = _VSTD::addressof(__that); 1152 if (__lhs->__move_nothrow() && !__rhs->__move_nothrow()) { 1153 _VSTD::swap(__lhs, __rhs); 1154 } 1155 __impl __tmp(_VSTD::move(*__rhs)); 1156#ifndef _LIBCPP_NO_EXCEPTIONS 1157 if constexpr (__all<is_nothrow_move_constructible_v<_Types>...>::value) { 1158 this->__generic_construct(*__rhs, _VSTD::move(*__lhs)); 1159 } else { 1160 // EXTENSION: When the move construction of `__lhs` into `__rhs` throws 1161 // and `__tmp` is nothrow move constructible then we move `__tmp` back 1162 // into `__rhs` and provide the strong exception safety guarantee. 1163 try { 1164 this->__generic_construct(*__rhs, _VSTD::move(*__lhs)); 1165 } catch (...) { 1166 if (__tmp.__move_nothrow()) { 1167 this->__generic_construct(*__rhs, _VSTD::move(__tmp)); 1168 } 1169 throw; 1170 } 1171 } 1172#else 1173 // this isn't consolidated with the `if constexpr` branch above due to 1174 // `throw` being ill-formed with exceptions disabled even when discarded. 1175 this->__generic_construct(*__rhs, _VSTD::move(*__lhs)); 1176#endif 1177 this->__generic_construct(*__lhs, _VSTD::move(__tmp)); 1178 } 1179 } 1180 1181private: 1182 inline _LIBCPP_INLINE_VISIBILITY 1183 bool __move_nothrow() const { 1184 constexpr bool __results[] = {is_nothrow_move_constructible_v<_Types>...}; 1185 return this->valueless_by_exception() || __results[this->index()]; 1186 } 1187}; 1188 1189struct __no_narrowing_check { 1190 template <class _Dest, class _Source> 1191 using _Apply = __identity<_Dest>; 1192}; 1193 1194struct __narrowing_check { 1195 template <class _Dest> 1196 static auto __test_impl(_Dest (&&)[1]) -> __identity<_Dest>; 1197 template <class _Dest, class _Source> 1198 using _Apply _LIBCPP_NODEBUG_TYPE = decltype(__test_impl<_Dest>({std::declval<_Source>()})); 1199}; 1200 1201template <class _Dest, class _Source> 1202using __check_for_narrowing _LIBCPP_NODEBUG_TYPE = 1203 typename _If< 1204#ifdef _LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT 1205 false && 1206#endif 1207 is_arithmetic<_Dest>::value, 1208 __narrowing_check, 1209 __no_narrowing_check 1210 >::template _Apply<_Dest, _Source>; 1211 1212template <class _Tp, size_t _Idx> 1213struct __overload { 1214 template <class _Up> 1215 auto operator()(_Tp, _Up&&) const -> __check_for_narrowing<_Tp, _Up>; 1216}; 1217 1218template <class _Tp, size_t> 1219struct __overload_bool { 1220 template <class _Up, class _Ap = __uncvref_t<_Up>> 1221 auto operator()(bool, _Up&&) const 1222 -> enable_if_t<is_same_v<_Ap, bool>, __identity<_Tp>>; 1223}; 1224 1225template <size_t _Idx> 1226struct __overload<bool, _Idx> : __overload_bool<bool, _Idx> {}; 1227template <size_t _Idx> 1228struct __overload<bool const, _Idx> : __overload_bool<bool const, _Idx> {}; 1229template <size_t _Idx> 1230struct __overload<bool volatile, _Idx> : __overload_bool<bool volatile, _Idx> {}; 1231template <size_t _Idx> 1232struct __overload<bool const volatile, _Idx> : __overload_bool<bool const volatile, _Idx> {}; 1233 1234template <class ..._Bases> 1235struct __all_overloads : _Bases... { 1236 void operator()() const; 1237 using _Bases::operator()...; 1238}; 1239 1240template <class IdxSeq> 1241struct __make_overloads_imp; 1242 1243template <size_t ..._Idx> 1244struct __make_overloads_imp<__tuple_indices<_Idx...> > { 1245 template <class ..._Types> 1246 using _Apply _LIBCPP_NODEBUG_TYPE = __all_overloads<__overload<_Types, _Idx>...>; 1247}; 1248 1249template <class ..._Types> 1250using _MakeOverloads _LIBCPP_NODEBUG_TYPE = typename __make_overloads_imp< 1251 __make_indices_imp<sizeof...(_Types), 0> >::template _Apply<_Types...>; 1252 1253template <class _Tp, class... _Types> 1254using __best_match_t = 1255 typename invoke_result_t<_MakeOverloads<_Types...>, _Tp, _Tp>::type; 1256 1257} // __variant_detail 1258 1259template <class... _Types> 1260class _LIBCPP_TEMPLATE_VIS variant 1261 : private __sfinae_ctor_base< 1262 __all<is_copy_constructible_v<_Types>...>::value, 1263 __all<is_move_constructible_v<_Types>...>::value>, 1264 private __sfinae_assign_base< 1265 __all<(is_copy_constructible_v<_Types> && 1266 is_copy_assignable_v<_Types>)...>::value, 1267 __all<(is_move_constructible_v<_Types> && 1268 is_move_assignable_v<_Types>)...>::value> { 1269 static_assert(0 < sizeof...(_Types), 1270 "variant must consist of at least one alternative."); 1271 1272 static_assert(__all<!is_array_v<_Types>...>::value, 1273 "variant can not have an array type as an alternative."); 1274 1275 static_assert(__all<!is_reference_v<_Types>...>::value, 1276 "variant can not have a reference type as an alternative."); 1277 1278 static_assert(__all<!is_void_v<_Types>...>::value, 1279 "variant can not have a void type as an alternative."); 1280 1281 using __first_type = variant_alternative_t<0, variant>; 1282 1283public: 1284 template <bool _Dummy = true, 1285 enable_if_t<__dependent_type<is_default_constructible<__first_type>, 1286 _Dummy>::value, 1287 int> = 0> 1288 inline _LIBCPP_INLINE_VISIBILITY 1289 constexpr variant() noexcept(is_nothrow_default_constructible_v<__first_type>) 1290 : __impl(in_place_index<0>) {} 1291 1292 variant(const variant&) = default; 1293 variant(variant&&) = default; 1294 1295 template < 1296 class _Arg, 1297 enable_if_t<!is_same_v<__uncvref_t<_Arg>, variant>, int> = 0, 1298 enable_if_t<!__is_inplace_type<__uncvref_t<_Arg>>::value, int> = 0, 1299 enable_if_t<!__is_inplace_index<__uncvref_t<_Arg>>::value, int> = 0, 1300 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>, 1301 size_t _Ip = 1302 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value, 1303 enable_if_t<is_constructible_v<_Tp, _Arg>, int> = 0> 1304 inline _LIBCPP_INLINE_VISIBILITY 1305 constexpr variant(_Arg&& __arg) noexcept( 1306 is_nothrow_constructible_v<_Tp, _Arg>) 1307 : __impl(in_place_index<_Ip>, _VSTD::forward<_Arg>(__arg)) {} 1308 1309 template <size_t _Ip, class... _Args, 1310 class = enable_if_t<(_Ip < sizeof...(_Types)), int>, 1311 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>, 1312 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0> 1313 inline _LIBCPP_INLINE_VISIBILITY 1314 explicit constexpr variant( 1315 in_place_index_t<_Ip>, 1316 _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, _Args...>) 1317 : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {} 1318 1319 template < 1320 size_t _Ip, 1321 class _Up, 1322 class... _Args, 1323 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0, 1324 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>, 1325 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, 1326 int> = 0> 1327 inline _LIBCPP_INLINE_VISIBILITY 1328 explicit constexpr variant( 1329 in_place_index_t<_Ip>, 1330 initializer_list<_Up> __il, 1331 _Args&&... __args) noexcept( 1332 is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>) 1333 : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {} 1334 1335 template < 1336 class _Tp, 1337 class... _Args, 1338 size_t _Ip = 1339 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value, 1340 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0> 1341 inline _LIBCPP_INLINE_VISIBILITY 1342 explicit constexpr variant(in_place_type_t<_Tp>, _Args&&... __args) noexcept( 1343 is_nothrow_constructible_v<_Tp, _Args...>) 1344 : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {} 1345 1346 template < 1347 class _Tp, 1348 class _Up, 1349 class... _Args, 1350 size_t _Ip = 1351 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value, 1352 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, 1353 int> = 0> 1354 inline _LIBCPP_INLINE_VISIBILITY 1355 explicit constexpr variant( 1356 in_place_type_t<_Tp>, 1357 initializer_list<_Up> __il, 1358 _Args&&... __args) noexcept( 1359 is_nothrow_constructible_v<_Tp, initializer_list< _Up>&, _Args...>) 1360 : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {} 1361 1362 ~variant() = default; 1363 1364 variant& operator=(const variant&) = default; 1365 variant& operator=(variant&&) = default; 1366 1367 template < 1368 class _Arg, 1369 enable_if_t<!is_same_v<__uncvref_t<_Arg>, variant>, int> = 0, 1370 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>, 1371 size_t _Ip = 1372 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value, 1373 enable_if_t<is_assignable_v<_Tp&, _Arg> && is_constructible_v<_Tp, _Arg>, 1374 int> = 0> 1375 inline _LIBCPP_INLINE_VISIBILITY 1376 variant& operator=(_Arg&& __arg) noexcept( 1377 is_nothrow_assignable_v<_Tp&, _Arg> && 1378 is_nothrow_constructible_v<_Tp, _Arg>) { 1379 __impl.template __assign<_Ip>(_VSTD::forward<_Arg>(__arg)); 1380 return *this; 1381 } 1382 1383 template < 1384 size_t _Ip, 1385 class... _Args, 1386 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0, 1387 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>, 1388 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0> 1389 inline _LIBCPP_INLINE_VISIBILITY 1390 _Tp& emplace(_Args&&... __args) { 1391 return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...); 1392 } 1393 1394 template < 1395 size_t _Ip, 1396 class _Up, 1397 class... _Args, 1398 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0, 1399 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>, 1400 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, 1401 int> = 0> 1402 inline _LIBCPP_INLINE_VISIBILITY 1403 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) { 1404 return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...); 1405 } 1406 1407 template < 1408 class _Tp, 1409 class... _Args, 1410 size_t _Ip = 1411 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value, 1412 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0> 1413 inline _LIBCPP_INLINE_VISIBILITY 1414 _Tp& emplace(_Args&&... __args) { 1415 return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...); 1416 } 1417 1418 template < 1419 class _Tp, 1420 class _Up, 1421 class... _Args, 1422 size_t _Ip = 1423 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value, 1424 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>, 1425 int> = 0> 1426 inline _LIBCPP_INLINE_VISIBILITY 1427 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) { 1428 return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...); 1429 } 1430 1431 inline _LIBCPP_INLINE_VISIBILITY 1432 constexpr bool valueless_by_exception() const noexcept { 1433 return __impl.valueless_by_exception(); 1434 } 1435 1436 inline _LIBCPP_INLINE_VISIBILITY 1437 constexpr size_t index() const noexcept { return __impl.index(); } 1438 1439 template < 1440 bool _Dummy = true, 1441 enable_if_t< 1442 __all<( 1443 __dependent_type<is_move_constructible<_Types>, _Dummy>::value && 1444 __dependent_type<is_swappable<_Types>, _Dummy>::value)...>::value, 1445 int> = 0> 1446 inline _LIBCPP_INLINE_VISIBILITY 1447 void swap(variant& __that) noexcept( 1448 __all<(is_nothrow_move_constructible_v<_Types> && 1449 is_nothrow_swappable_v<_Types>)...>::value) { 1450 __impl.__swap(__that.__impl); 1451 } 1452 1453private: 1454 __variant_detail::__impl<_Types...> __impl; 1455 1456 friend struct __variant_detail::__access::__variant; 1457 friend struct __variant_detail::__visitation::__variant; 1458}; 1459 1460template <size_t _Ip, class... _Types> 1461inline _LIBCPP_INLINE_VISIBILITY 1462constexpr bool __holds_alternative(const variant<_Types...>& __v) noexcept { 1463 return __v.index() == _Ip; 1464} 1465 1466template <class _Tp, class... _Types> 1467inline _LIBCPP_INLINE_VISIBILITY 1468constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept { 1469 return __holds_alternative<__find_exactly_one_t<_Tp, _Types...>::value>(__v); 1470} 1471 1472template <size_t _Ip, class _Vp> 1473inline _LIBCPP_INLINE_VISIBILITY 1474_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1475constexpr auto&& __generic_get(_Vp&& __v) { 1476 using __variant_detail::__access::__variant; 1477 if (!__holds_alternative<_Ip>(__v)) { 1478 __throw_bad_variant_access(); 1479 } 1480 return __variant::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v)).__value; 1481} 1482 1483template <size_t _Ip, class... _Types> 1484inline _LIBCPP_INLINE_VISIBILITY 1485_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1486constexpr variant_alternative_t<_Ip, variant<_Types...>>& get( 1487 variant<_Types...>& __v) { 1488 static_assert(_Ip < sizeof...(_Types)); 1489 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>); 1490 return __generic_get<_Ip>(__v); 1491} 1492 1493template <size_t _Ip, class... _Types> 1494inline _LIBCPP_INLINE_VISIBILITY 1495_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1496constexpr variant_alternative_t<_Ip, variant<_Types...>>&& get( 1497 variant<_Types...>&& __v) { 1498 static_assert(_Ip < sizeof...(_Types)); 1499 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>); 1500 return __generic_get<_Ip>(_VSTD::move(__v)); 1501} 1502 1503template <size_t _Ip, class... _Types> 1504inline _LIBCPP_INLINE_VISIBILITY 1505_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1506constexpr const variant_alternative_t<_Ip, variant<_Types...>>& get( 1507 const variant<_Types...>& __v) { 1508 static_assert(_Ip < sizeof...(_Types)); 1509 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>); 1510 return __generic_get<_Ip>(__v); 1511} 1512 1513template <size_t _Ip, class... _Types> 1514inline _LIBCPP_INLINE_VISIBILITY 1515_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1516constexpr const variant_alternative_t<_Ip, variant<_Types...>>&& get( 1517 const variant<_Types...>&& __v) { 1518 static_assert(_Ip < sizeof...(_Types)); 1519 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>); 1520 return __generic_get<_Ip>(_VSTD::move(__v)); 1521} 1522 1523template <class _Tp, class... _Types> 1524inline _LIBCPP_INLINE_VISIBILITY 1525_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1526constexpr _Tp& get(variant<_Types...>& __v) { 1527 static_assert(!is_void_v<_Tp>); 1528 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v); 1529} 1530 1531template <class _Tp, class... _Types> 1532inline _LIBCPP_INLINE_VISIBILITY 1533_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1534constexpr _Tp&& get(variant<_Types...>&& __v) { 1535 static_assert(!is_void_v<_Tp>); 1536 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>( 1537 _VSTD::move(__v)); 1538} 1539 1540template <class _Tp, class... _Types> 1541inline _LIBCPP_INLINE_VISIBILITY 1542_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1543constexpr const _Tp& get(const variant<_Types...>& __v) { 1544 static_assert(!is_void_v<_Tp>); 1545 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v); 1546} 1547 1548template <class _Tp, class... _Types> 1549inline _LIBCPP_INLINE_VISIBILITY 1550_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1551constexpr const _Tp&& get(const variant<_Types...>&& __v) { 1552 static_assert(!is_void_v<_Tp>); 1553 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>( 1554 _VSTD::move(__v)); 1555} 1556 1557template <size_t _Ip, class _Vp> 1558inline _LIBCPP_INLINE_VISIBILITY 1559constexpr auto* __generic_get_if(_Vp* __v) noexcept { 1560 using __variant_detail::__access::__variant; 1561 return __v && __holds_alternative<_Ip>(*__v) 1562 ? _VSTD::addressof(__variant::__get_alt<_Ip>(*__v).__value) 1563 : nullptr; 1564} 1565 1566template <size_t _Ip, class... _Types> 1567inline _LIBCPP_INLINE_VISIBILITY 1568constexpr add_pointer_t<variant_alternative_t<_Ip, variant<_Types...>>> 1569get_if(variant<_Types...>* __v) noexcept { 1570 static_assert(_Ip < sizeof...(_Types)); 1571 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>); 1572 return __generic_get_if<_Ip>(__v); 1573} 1574 1575template <size_t _Ip, class... _Types> 1576inline _LIBCPP_INLINE_VISIBILITY 1577constexpr add_pointer_t<const variant_alternative_t<_Ip, variant<_Types...>>> 1578get_if(const variant<_Types...>* __v) noexcept { 1579 static_assert(_Ip < sizeof...(_Types)); 1580 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>); 1581 return __generic_get_if<_Ip>(__v); 1582} 1583 1584template <class _Tp, class... _Types> 1585inline _LIBCPP_INLINE_VISIBILITY 1586constexpr add_pointer_t<_Tp> 1587get_if(variant<_Types...>* __v) noexcept { 1588 static_assert(!is_void_v<_Tp>); 1589 return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v); 1590} 1591 1592template <class _Tp, class... _Types> 1593inline _LIBCPP_INLINE_VISIBILITY 1594constexpr add_pointer_t<const _Tp> 1595get_if(const variant<_Types...>* __v) noexcept { 1596 static_assert(!is_void_v<_Tp>); 1597 return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v); 1598} 1599 1600template <class _Operator> 1601struct __convert_to_bool { 1602 template <class _T1, class _T2> 1603 _LIBCPP_INLINE_VISIBILITY constexpr bool operator()(_T1 && __t1, _T2&& __t2) const { 1604 static_assert(std::is_convertible<decltype(_Operator{}(_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2))), bool>::value, 1605 "the relational operator does not return a type which is implicitly convertible to bool"); 1606 return _Operator{}(_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2)); 1607 } 1608}; 1609 1610template <class... _Types> 1611inline _LIBCPP_INLINE_VISIBILITY 1612constexpr bool operator==(const variant<_Types...>& __lhs, 1613 const variant<_Types...>& __rhs) { 1614 using __variant_detail::__visitation::__variant; 1615 if (__lhs.index() != __rhs.index()) return false; 1616 if (__lhs.valueless_by_exception()) return true; 1617 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<equal_to<>>{}, __lhs, __rhs); 1618} 1619 1620template <class... _Types> 1621inline _LIBCPP_INLINE_VISIBILITY 1622constexpr bool operator!=(const variant<_Types...>& __lhs, 1623 const variant<_Types...>& __rhs) { 1624 using __variant_detail::__visitation::__variant; 1625 if (__lhs.index() != __rhs.index()) return true; 1626 if (__lhs.valueless_by_exception()) return false; 1627 return __variant::__visit_value_at( 1628 __lhs.index(), __convert_to_bool<not_equal_to<>>{}, __lhs, __rhs); 1629} 1630 1631template <class... _Types> 1632inline _LIBCPP_INLINE_VISIBILITY 1633constexpr bool operator<(const variant<_Types...>& __lhs, 1634 const variant<_Types...>& __rhs) { 1635 using __variant_detail::__visitation::__variant; 1636 if (__rhs.valueless_by_exception()) return false; 1637 if (__lhs.valueless_by_exception()) return true; 1638 if (__lhs.index() < __rhs.index()) return true; 1639 if (__lhs.index() > __rhs.index()) return false; 1640 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<less<>>{}, __lhs, __rhs); 1641} 1642 1643template <class... _Types> 1644inline _LIBCPP_INLINE_VISIBILITY 1645constexpr bool operator>(const variant<_Types...>& __lhs, 1646 const variant<_Types...>& __rhs) { 1647 using __variant_detail::__visitation::__variant; 1648 if (__lhs.valueless_by_exception()) return false; 1649 if (__rhs.valueless_by_exception()) return true; 1650 if (__lhs.index() > __rhs.index()) return true; 1651 if (__lhs.index() < __rhs.index()) return false; 1652 return __variant::__visit_value_at(__lhs.index(), __convert_to_bool<greater<>>{}, __lhs, __rhs); 1653} 1654 1655template <class... _Types> 1656inline _LIBCPP_INLINE_VISIBILITY 1657constexpr bool operator<=(const variant<_Types...>& __lhs, 1658 const variant<_Types...>& __rhs) { 1659 using __variant_detail::__visitation::__variant; 1660 if (__lhs.valueless_by_exception()) return true; 1661 if (__rhs.valueless_by_exception()) return false; 1662 if (__lhs.index() < __rhs.index()) return true; 1663 if (__lhs.index() > __rhs.index()) return false; 1664 return __variant::__visit_value_at( 1665 __lhs.index(), __convert_to_bool<less_equal<>>{}, __lhs, __rhs); 1666} 1667 1668template <class... _Types> 1669inline _LIBCPP_INLINE_VISIBILITY 1670constexpr bool operator>=(const variant<_Types...>& __lhs, 1671 const variant<_Types...>& __rhs) { 1672 using __variant_detail::__visitation::__variant; 1673 if (__rhs.valueless_by_exception()) return true; 1674 if (__lhs.valueless_by_exception()) return false; 1675 if (__lhs.index() > __rhs.index()) return true; 1676 if (__lhs.index() < __rhs.index()) return false; 1677 return __variant::__visit_value_at( 1678 __lhs.index(), __convert_to_bool<greater_equal<>>{}, __lhs, __rhs); 1679} 1680 1681template <class _Vis, class... _Vs> 1682inline _LIBCPP_INLINE_VISIBILITY 1683_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 1684constexpr decltype(auto) visit(_Vis&& __vis, _Vs&&... __vs) { 1685 using __variant_detail::__visitation::__variant; 1686 return __variant::__visit_value(_VSTD::forward<_Vis>(__vis), 1687 _VSTD::forward<_Vs>(__vs)...); 1688} 1689 1690struct _LIBCPP_TEMPLATE_VIS monostate {}; 1691 1692inline _LIBCPP_INLINE_VISIBILITY 1693constexpr bool operator<(monostate, monostate) noexcept { return false; } 1694 1695inline _LIBCPP_INLINE_VISIBILITY 1696constexpr bool operator>(monostate, monostate) noexcept { return false; } 1697 1698inline _LIBCPP_INLINE_VISIBILITY 1699constexpr bool operator<=(monostate, monostate) noexcept { return true; } 1700 1701inline _LIBCPP_INLINE_VISIBILITY 1702constexpr bool operator>=(monostate, monostate) noexcept { return true; } 1703 1704inline _LIBCPP_INLINE_VISIBILITY 1705constexpr bool operator==(monostate, monostate) noexcept { return true; } 1706 1707inline _LIBCPP_INLINE_VISIBILITY 1708constexpr bool operator!=(monostate, monostate) noexcept { return false; } 1709 1710template <class... _Types> 1711inline _LIBCPP_INLINE_VISIBILITY 1712auto swap(variant<_Types...>& __lhs, 1713 variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs))) 1714 -> decltype(__lhs.swap(__rhs)) { 1715 __lhs.swap(__rhs); 1716} 1717 1718template <class... _Types> 1719struct _LIBCPP_TEMPLATE_VIS hash< 1720 __enable_hash_helper<variant<_Types...>, remove_const_t<_Types>...>> { 1721 using argument_type = variant<_Types...>; 1722 using result_type = size_t; 1723 1724 inline _LIBCPP_INLINE_VISIBILITY 1725 result_type operator()(const argument_type& __v) const { 1726 using __variant_detail::__visitation::__variant; 1727 size_t __res = 1728 __v.valueless_by_exception() 1729 ? 299792458 // Random value chosen by the universe upon creation 1730 : __variant::__visit_alt( 1731 [](const auto& __alt) { 1732 using __alt_type = __uncvref_t<decltype(__alt)>; 1733 using __value_type = remove_const_t< 1734 typename __alt_type::__value_type>; 1735 return hash<__value_type>{}(__alt.__value); 1736 }, 1737 __v); 1738 return __hash_combine(__res, hash<size_t>{}(__v.index())); 1739 } 1740}; 1741 1742template <> 1743struct _LIBCPP_TEMPLATE_VIS hash<monostate> { 1744 using argument_type = monostate; 1745 using result_type = size_t; 1746 1747 inline _LIBCPP_INLINE_VISIBILITY 1748 result_type operator()(const argument_type&) const _NOEXCEPT { 1749 return 66740831; // return a fundamentally attractive random value. 1750 } 1751}; 1752 1753#endif // _LIBCPP_STD_VER > 14 1754 1755_LIBCPP_END_NAMESPACE_STD 1756 1757_LIBCPP_POP_MACROS 1758 1759#endif // _LIBCPP_VARIANT 1760