Implement C++17 <variant>. Patch from Michael Park!
This patch was reviewed as https://reviews.llvm.org/D23263.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@288547 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/variant b/include/variant
new file mode 100644
index 0000000..f57d5ce
--- /dev/null
+++ b/include/variant
@@ -0,0 +1,1553 @@
+// -*- C++ -*-
+//===------------------------------ variant -------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_VARIANT
+#define _LIBCPP_VARIANT
+
+/*
+ variant synopsis
+
+namespace std {
+
+ // 20.7.2, class template variant
+ template <class... Types>
+ class variant {
+ public:
+
+ // 20.7.2.1, constructors
+ constexpr variant() noexcept(see below);
+ variant(const variant&);
+ variant(variant&&) noexcept(see below);
+
+ template <class T> constexpr variant(T&&) noexcept(see below);
+
+ template <class T, class... Args>
+ constexpr explicit variant(in_place_type_t<T>, Args&&...);
+
+ template <class T, class U, class... Args>
+ constexpr explicit variant(
+ in_place_type_t<T>, initializer_list<U>, Args&&...);
+
+ template <size_t I, class... Args>
+ constexpr explicit variant(in_place_index_t<I>, Args&&...);
+
+ template <size_t I, class U, class... Args>
+ constexpr explicit variant(
+ in_place_index_t<I>, initializer_list<U>, Args&&...);
+
+ // 20.7.2.2, destructor
+ ~variant();
+
+ // 20.7.2.3, assignment
+ variant& operator=(const variant&);
+ variant& operator=(variant&&) noexcept(see below);
+
+ template <class T> variant& operator=(T&&) noexcept(see below);
+
+ // 20.7.2.4, modifiers
+ template <class T, class... Args>
+ void emplace(Args&&...);
+
+ template <class T, class U, class... Args>
+ void emplace(initializer_list<U>, Args&&...);
+
+ template <size_t I, class... Args>
+ void emplace(Args&&...);
+
+ template <size_t I, class U, class... Args>
+ void emplace(initializer_list<U>, Args&&...);
+
+ // 20.7.2.5, value status
+ constexpr bool valueless_by_exception() const noexcept;
+ constexpr size_t index() const noexcept;
+
+ // 20.7.2.6, swap
+ void swap(variant&) noexcept(see below);
+ };
+
+ // 20.7.3, variant helper classes
+ template <class T> struct variant_size; // undefined
+
+ template <class T>
+ constexpr size_t variant_size_v = variant_size<T>::value;
+
+ template <class T> struct variant_size<const T>;
+ template <class T> struct variant_size<volatile T>;
+ template <class T> struct variant_size<const volatile T>;
+
+ template <class... Types>
+ struct variant_size<variant<Types...>>;
+
+ template <size_t I, class T> struct variant_alternative; // undefined
+
+ template <size_t I, class T>
+ using variant_alternative_t = typename variant_alternative<I, T>::type;
+
+ template <size_t I, class T> struct variant_alternative<I, const T>;
+ template <size_t I, class T> struct variant_alternative<I, volatile T>;
+ template <size_t I, class T> struct variant_alternative<I, const volatile T>;
+
+ template <size_t I, class... Types>
+ struct variant_alternative<I, variant<Types...>>;
+
+ constexpr size_t variant_npos = -1;
+
+ // 20.7.4, value access
+ template <class T, class... Types>
+ constexpr bool holds_alternative(const variant<Types...>&) noexcept;
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>>&
+ get(variant<Types...>&);
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>>&&
+ get(variant<Types...>&&);
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>> const&
+ get(const variant<Types...>&);
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>> const&&
+ get(const variant<Types...>&&);
+
+ template <class T, class... Types>
+ constexpr T& get(variant<Types...>&);
+
+ template <class T, class... Types>
+ constexpr T&& get(variant<Types...>&&);
+
+ template <class T, class... Types>
+ constexpr const T& get(const variant<Types...>&);
+
+ template <class T, class... Types>
+ constexpr const T&& get(const variant<Types...>&&);
+
+ template <size_t I, class... Types>
+ constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>>
+ get_if(variant<Types...>*) noexcept;
+
+ template <size_t I, class... Types>
+ constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>>
+ get_if(const variant<Types...>*) noexcept;
+
+ template <class T, class... Types>
+ constexpr add_pointer_t<T>
+ get_if(variant<Types...>*) noexcept;
+
+ template <class T, class... Types>
+ constexpr add_pointer_t<const T>
+ get_if(const variant<Types...>*) noexcept;
+
+ // 20.7.5, relational operators
+ template <class... Types>
+ constexpr bool operator==(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator!=(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator<(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator>(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator<=(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator>=(const variant<Types...>&, const variant<Types...>&);
+
+ // 20.7.6, visitation
+ template <class Visitor, class... Variants>
+ constexpr see below visit(Visitor&&, Variants&&...);
+
+ // 20.7.7, class monostate
+ struct monostate;
+
+ // 20.7.8, monostate relational operators
+ constexpr bool operator<(monostate, monostate) noexcept;
+ constexpr bool operator>(monostate, monostate) noexcept;
+ constexpr bool operator<=(monostate, monostate) noexcept;
+ constexpr bool operator>=(monostate, monostate) noexcept;
+ constexpr bool operator==(monostate, monostate) noexcept;
+ constexpr bool operator!=(monostate, monostate) noexcept;
+
+ // 20.7.9, specialized algorithms
+ template <class... Types>
+ void swap(variant<Types...>&, variant<Types...>&) noexcept(see below);
+
+ // 20.7.10, class bad_variant_access
+ class bad_variant_access;
+
+ // 20.7.11, hash support
+ template <class T> struct hash;
+ template <class... Types> struct hash<variant<Types...>>;
+ template <> struct hash<monostate>;
+
+} // namespace std
+
+*/
+
+#include <__config>
+#include <__tuple>
+#include <array>
+#include <exception>
+#include <functional>
+#include <initializer_list>
+#include <new>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+namespace std { // explicitly not using versioning namespace
+
+class _LIBCPP_EXCEPTION_ABI bad_variant_access : public exception {
+public:
+ _LIBCPP_FUNC_VIS virtual const char* what() const noexcept;
+};
+
+} // namespace std
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 14
+
+template <class... _Types>
+class _LIBCPP_TYPE_VIS_ONLY variant;
+
+template <class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_size;
+
+template <class _Tp>
+constexpr size_t variant_size_v = variant_size<_Tp>::value;
+
+template <class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_size<const _Tp> : variant_size<_Tp> {};
+
+template <class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_size<volatile _Tp> : variant_size<_Tp> {};
+
+template <class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_size<const volatile _Tp>
+ : variant_size<_Tp> {};
+
+template <class... _Types>
+struct _LIBCPP_TYPE_VIS_ONLY variant_size<variant<_Types...>>
+ : integral_constant<size_t, sizeof...(_Types)> {};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_alternative;
+
+template <size_t _Ip, class _Tp>
+using variant_alternative_t = typename variant_alternative<_Ip, _Tp>::type;
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_alternative<_Ip, const _Tp>
+ : add_const<variant_alternative_t<_Ip, _Tp>> {};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_alternative<_Ip, volatile _Tp>
+ : add_volatile<variant_alternative_t<_Ip, _Tp>> {};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY variant_alternative<_Ip, const volatile _Tp>
+ : add_cv<variant_alternative_t<_Ip, _Tp>> {};
+
+template <size_t _Ip, class... _Types>
+struct _LIBCPP_TYPE_VIS_ONLY variant_alternative<_Ip, variant<_Types...>> {
+ static_assert(_Ip < sizeof...(_Types));
+ using type = __type_pack_element<_Ip, _Types...>;
+};
+
+constexpr size_t variant_npos = static_cast<size_t>(-1);
+constexpr unsigned int __variant_npos = static_cast<unsigned int>(-1);
+
+namespace __find_detail {
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr size_t __find_index() {
+ constexpr bool __matches[] = {is_same_v<_Tp, _Types>...};
+ size_t __result = __not_found;
+ for (size_t __i = 0; __i < sizeof...(_Types); ++__i) {
+ if (__matches[__i]) {
+ if (__result != __not_found) {
+ return __ambiguous;
+ }
+ __result = __i;
+ }
+ }
+ return __result;
+}
+
+template <size_t _Index>
+struct __find_unambiguous_index_sfinae_impl
+ : integral_constant<size_t, _Index> {};
+
+template <>
+struct __find_unambiguous_index_sfinae_impl<__not_found> {};
+
+template <>
+struct __find_unambiguous_index_sfinae_impl<__ambiguous> {};
+
+template <class _Tp, class... _Types>
+struct __find_unambiguous_index_sfinae
+ : __find_unambiguous_index_sfinae_impl<__find_index<_Tp, _Types...>()> {};
+
+} // namespace __find_detail
+
+namespace __variant_detail {
+
+struct __valueless_t {};
+
+enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
+
+template <typename _Tp,
+ template <typename> class _IsTriviallyAvailable,
+ template <typename> class _IsAvailable>
+constexpr _Trait __trait =
+ _IsTriviallyAvailable<_Tp>::value
+ ? _Trait::_TriviallyAvailable
+ : _IsAvailable<_Tp>::value ? _Trait::_Available : _Trait::_Unavailable;
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Trait __common_trait(initializer_list<_Trait> __traits) {
+ _Trait __result = _Trait::_TriviallyAvailable;
+ for (_Trait __t : __traits) {
+ if (static_cast<int>(__t) > static_cast<int>(__result)) {
+ __result = __t;
+ }
+ }
+ return __result;
+}
+
+template <typename... _Types>
+struct __traits {
+ static constexpr _Trait __copy_constructible_trait =
+ __common_trait({__trait<_Types,
+ is_trivially_copy_constructible,
+ is_copy_constructible>...});
+
+ static constexpr _Trait __move_constructible_trait =
+ __common_trait({__trait<_Types,
+ is_trivially_move_constructible,
+ is_move_constructible>...});
+
+ static constexpr _Trait __copy_assignable_trait = __common_trait(
+ {__copy_constructible_trait,
+ __move_constructible_trait,
+ __trait<_Types, is_trivially_copy_assignable, is_copy_assignable>...});
+
+ static constexpr _Trait __move_assignable_trait = __common_trait(
+ {__move_constructible_trait,
+ __trait<_Types, is_trivially_move_assignable, is_move_assignable>...});
+
+ static constexpr _Trait __destructible_trait = __common_trait(
+ {__trait<_Types, is_trivially_destructible, is_destructible>...});
+};
+
+namespace __access {
+
+struct __union {
+ template <class _Vp>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<0>) {
+ return _VSTD::forward<_Vp>(__v).__head;
+ }
+
+ template <class _Vp, size_t _Ip>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<_Ip>) {
+ return __get_alt(_VSTD::forward<_Vp>(__v).__tail, in_place_index<_Ip - 1>);
+ }
+};
+
+struct __base {
+ template <size_t _Ip, class _Vp>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto&& __get_alt(_Vp&& __v) {
+ return __union::__get_alt(_VSTD::forward<_Vp>(__v).__data,
+ in_place_index<_Ip>);
+ }
+};
+
+struct __variant {
+ template <size_t _Ip, class _Vp>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto&& __get_alt(_Vp&& __v) {
+ return __base::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v).__impl);
+ }
+};
+
+} // namespace __access
+
+namespace __visitation {
+
+struct __base {
+ template <class _Visitor, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr decltype(auto)
+ __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+ constexpr auto __fdiagonal =
+ __make_fdiagonal<_Visitor&&,
+ decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
+ return __fdiagonal[__index](_VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs).__as_base()...);
+ }
+
+ template <class _Visitor, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
+ _Vs&&... __vs) {
+ constexpr auto __fmatrix =
+ __make_fmatrix<_Visitor&&,
+ decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
+ const size_t __indices[] = {__vs.index()...};
+ return __at(__fmatrix, __indices)(_VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs).__as_base()...);
+ }
+
+private:
+ template <class _Tp>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr const _Tp& __at_impl(const _Tp& __elem, const size_t*) {
+ return __elem;
+ }
+
+ template <class _Tp, size_t _Np>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto&& __at_impl(const array<_Tp, _Np>& __elems,
+ const size_t* __index) {
+ return __at_impl(__elems[*__index], __index + 1);
+ }
+
+ template <class _Tp, size_t _Np, size_t _Ip>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto&& __at(const array<_Tp, _Np>& __elems,
+ const size_t (&__indices)[_Ip]) {
+ return __at_impl(__elems, begin(__indices));
+ }
+
+ template <class _Fp, class... _Fs>
+ static constexpr void __std_visit_visitor_return_type_check() {
+ static_assert(
+ __all<is_same_v<_Fp, _Fs>...>::value,
+ "`std::visit` requires the visitor to have a single return type.");
+ }
+
+ template <class... _Fs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_farray(_Fs&&... __fs) {
+ __std_visit_visitor_return_type_check<decay_t<_Fs>...>();
+ using __result = array<common_type_t<decay_t<_Fs>...>, sizeof...(_Fs)>;
+ return __result{_VSTD::forward<_Fs>(__fs)...};
+ }
+
+ template <class _Fp, class... _Vs, size_t... _Is>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_dispatch(index_sequence<_Is...>) {
+ struct __dispatcher {
+ static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
+ return __invoke_constexpr(
+ static_cast<_Fp>(__f),
+ __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
+ }
+ };
+ return _VSTD::addressof(__dispatcher::__dispatch);
+ }
+
+ template <size_t _Ip, class _Fp, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fdiagonal_impl() {
+ return __make_dispatch<_Fp, _Vs...>(
+ index_sequence<(__identity<_Vs>{}, _Ip)...>{});
+ }
+
+ template <class _Fp, class... _Vs, size_t... _Is>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
+ return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
+ }
+
+ template <class _Fp, class _Vp, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fdiagonal() {
+ constexpr size_t _Np = decay_t<_Vp>::__size();
+ static_assert(__all<(_Np == decay_t<_Vs>::__size())...>::value);
+ return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<_Np>{});
+ }
+
+ template <class _Fp, class... _Vs, size_t... _Is>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
+ return __make_dispatch<_Fp, _Vs...>(__is);
+ }
+
+ template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fmatrix_impl(index_sequence<_Is...>,
+ index_sequence<_Js...>,
+ _Ls... __ls) {
+ return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(
+ index_sequence<_Is..., _Js>{}, __ls...)...);
+ }
+
+ template <class _Fp, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fmatrix() {
+ return __make_fmatrix_impl<_Fp, _Vs...>(
+ index_sequence<>{}, make_index_sequence<decay_t<_Vs>::__size()>{}...);
+ }
+};
+
+struct __variant {
+ template <class _Visitor, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr decltype(auto)
+ __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+ return __base::__visit_alt_at(__index,
+ _VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs).__impl...);
+ }
+
+ template <class _Visitor, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
+ _Vs&&... __vs) {
+ return __base::__visit_alt(_VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs).__impl...);
+ }
+
+ template <class _Visitor, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr decltype(auto)
+ __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+ return __visit_alt_at(
+ __index,
+ __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
+ _VSTD::forward<_Vs>(__vs)...);
+ }
+
+ template <class _Visitor, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr decltype(auto) __visit_value(_Visitor&& __visitor,
+ _Vs&&... __vs) {
+ return __visit_alt(
+ __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
+ _VSTD::forward<_Vs>(__vs)...);
+ }
+
+private:
+ template <class _Visitor, class... _Values>
+ static constexpr void __std_visit_exhaustive_visitor_check() {
+ static_assert(is_callable_v<_Visitor(_Values...)>,
+ "`std::visit` requires the visitor to be exhaustive.");
+ }
+
+ template <class _Visitor>
+ struct __value_visitor {
+ template <class... _Alts>
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr decltype(auto) operator()(_Alts&&... __alts) const {
+ __std_visit_exhaustive_visitor_check<
+ _Visitor,
+ decltype(_VSTD::forward<_Alts>(__alts).__value)...>();
+ return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Alts>(__alts).__value...);
+ }
+ _Visitor&& __visitor;
+ };
+
+ template <class _Visitor>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
+ return __value_visitor<_Visitor>{_VSTD::forward<_Visitor>(__visitor)};
+ }
+};
+
+} // namespace __visitation
+
+template <size_t _Index, class _Tp>
+struct _LIBCPP_TYPE_VIS_ONLY __alt {
+ using __value_type = _Tp;
+
+ template <class... _Args>
+ inline _LIBCPP_INLINE_VISIBILITY
+ explicit constexpr __alt(in_place_t, _Args&&... __args)
+ : __value(_VSTD::forward<_Args>(__args)...) {}
+
+ __value_type __value;
+};
+
+template <_Trait _DestructibleTrait, size_t _Index, class... _Types>
+union _LIBCPP_TYPE_VIS_ONLY __union;
+
+template <_Trait _DestructibleTrait, size_t _Index>
+union _LIBCPP_TYPE_VIS_ONLY __union<_DestructibleTrait, _Index> {};
+
+#define _LIBCPP_VARIANT_UNION(destructible_trait, destructor) \
+ template <size_t _Index, class _Tp, class... _Types> \
+ union _LIBCPP_TYPE_VIS_ONLY __union<destructible_trait, \
+ _Index, \
+ _Tp, \
+ _Types...> { \
+ public: \
+ inline _LIBCPP_INLINE_VISIBILITY \
+ explicit constexpr __union(__valueless_t) noexcept : __dummy{} {} \
+ \
+ template <class... _Args> \
+ inline _LIBCPP_INLINE_VISIBILITY \
+ explicit constexpr __union(in_place_index_t<0>, _Args&&... __args) \
+ : __head(in_place, _VSTD::forward<_Args>(__args)...) {} \
+ \
+ template <size_t _Ip, class... _Args> \
+ inline _LIBCPP_INLINE_VISIBILITY \
+ explicit constexpr __union(in_place_index_t<_Ip>, _Args&&... __args) \
+ : __tail(in_place_index<_Ip - 1>, _VSTD::forward<_Args>(__args)...) {} \
+ \
+ __union(const __union&) = default; \
+ __union(__union&&) = default; \
+ \
+ destructor \
+ \
+ __union& operator=(const __union&) = default; \
+ __union& operator=(__union&&) = default; \
+ \
+ private: \
+ char __dummy; \
+ __alt<_Index, _Tp> __head; \
+ __union<destructible_trait, _Index + 1, _Types...> __tail; \
+ \
+ friend struct __access::__union; \
+ }
+
+_LIBCPP_VARIANT_UNION(_Trait::_TriviallyAvailable, ~__union() = default;);
+_LIBCPP_VARIANT_UNION(_Trait::_Available, ~__union() {});
+_LIBCPP_VARIANT_UNION(_Trait::_Unavailable, ~__union() = delete;);
+
+#undef _LIBCPP_VARIANT_UNION
+
+template <_Trait _DestructibleTrait, class... _Types>
+class _LIBCPP_TYPE_VIS_ONLY __base {
+public:
+ inline _LIBCPP_INLINE_VISIBILITY
+ explicit constexpr __base(__valueless_t tag) noexcept
+ : __index(__variant_npos), __data(tag) {}
+
+ template <size_t _Ip, class... _Args>
+ inline _LIBCPP_INLINE_VISIBILITY
+ explicit constexpr __base(in_place_index_t<_Ip>, _Args&&... __args)
+ : __index(_Ip),
+ __data(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr bool valueless_by_exception() const noexcept {
+ return index() == variant_npos;
+ }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr size_t index() const noexcept {
+ return __index == __variant_npos ? variant_npos : __index;
+ }
+
+protected:
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr auto&& __as_base() & { return *this; }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr auto&& __as_base() && { return _VSTD::move(*this); }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr auto&& __as_base() const & { return *this; }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr auto&& __as_base() const && { return _VSTD::move(*this); }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr size_t __size() { return sizeof...(_Types); }
+
+ __union<_DestructibleTrait, 0, _Types...> __data;
+ unsigned int __index;
+
+ friend struct __access::__base;
+ friend struct __visitation::__base;
+};
+
+template <class _Traits, _Trait = _Traits::__destructible_trait>
+class _LIBCPP_TYPE_VIS_ONLY __destructor;
+
+#define _LIBCPP_VARIANT_DESTRUCTOR(destructible_trait, destructor, destroy) \
+ template <class... _Types> \
+ class _LIBCPP_TYPE_VIS_ONLY __destructor<__traits<_Types...>, \
+ destructible_trait> \
+ : public __base<destructible_trait, _Types...> { \
+ using __base_type = __base<destructible_trait, _Types...>; \
+ \
+ public: \
+ using __base_type::__base_type; \
+ using __base_type::operator=; \
+ \
+ __destructor(const __destructor&) = default; \
+ __destructor(__destructor&&) = default; \
+ destructor \
+ __destructor& operator=(const __destructor&) = default; \
+ __destructor& operator=(__destructor&&) = default; \
+ \
+ protected: \
+ inline _LIBCPP_INLINE_VISIBILITY \
+ destroy \
+ }
+
+_LIBCPP_VARIANT_DESTRUCTOR(
+ _Trait::_TriviallyAvailable,
+ ~__destructor() = default;,
+ void __destroy() noexcept { this->__index = __variant_npos; });
+
+_LIBCPP_VARIANT_DESTRUCTOR(
+ _Trait::_Available,
+ ~__destructor() { __destroy(); },
+ void __destroy() noexcept {
+ if (!this->valueless_by_exception()) {
+ __visitation::__base::__visit_alt(
+ [](auto& __alt) noexcept {
+ using __alt_type = decay_t<decltype(__alt)>;
+ __alt.~__alt_type();
+ },
+ *this);
+ }
+ this->__index = __variant_npos;
+ });
+
+_LIBCPP_VARIANT_DESTRUCTOR(
+ _Trait::_Unavailable,
+ ~__destructor() = delete;,
+ void __destroy() noexcept = delete;);
+
+#undef _LIBCPP_VARIANT_DESTRUCTOR
+
+template <class _Traits>
+class _LIBCPP_TYPE_VIS_ONLY __constructor : public __destructor<_Traits> {
+ using __base_type = __destructor<_Traits>;
+
+public:
+ using __base_type::__base_type;
+ using __base_type::operator=;
+
+protected:
+ template <size_t _Ip, class _Tp, class... _Args>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static void __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) {
+ ::new (_VSTD::addressof(__a))
+ __alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
+ }
+
+ template <class _Rhs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static void __generic_construct(__constructor& __lhs, _Rhs&& __rhs) {
+ __lhs.__destroy();
+ if (!__rhs.valueless_by_exception()) {
+ __visitation::__base::__visit_alt_at(
+ __rhs.index(),
+ [](auto& __lhs_alt, auto&& __rhs_alt) {
+ __construct_alt(
+ __lhs_alt,
+ _VSTD::forward<decltype(__rhs_alt)>(__rhs_alt).__value);
+ },
+ __lhs, _VSTD::forward<_Rhs>(__rhs));
+ __lhs.__index = __rhs.index();
+ }
+ }
+};
+
+template <class _Traits, _Trait = _Traits::__move_constructible_trait>
+class _LIBCPP_TYPE_VIS_ONLY __move_constructor;
+
+#define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, \
+ move_constructor) \
+ template <class... _Types> \
+ class _LIBCPP_TYPE_VIS_ONLY __move_constructor<__traits<_Types...>, \
+ move_constructible_trait> \
+ : public __constructor<__traits<_Types...>> { \
+ using __base_type = __constructor<__traits<_Types...>>; \
+ \
+ public: \
+ using __base_type::__base_type; \
+ using __base_type::operator=; \
+ \
+ __move_constructor(const __move_constructor&) = default; \
+ move_constructor \
+ ~__move_constructor() = default; \
+ __move_constructor& operator=(const __move_constructor&) = default; \
+ __move_constructor& operator=(__move_constructor&&) = default; \
+ }
+
+_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
+ _Trait::_TriviallyAvailable,
+ __move_constructor(__move_constructor&& __that) = default;);
+
+_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
+ _Trait::_Available,
+ __move_constructor(__move_constructor&& __that) noexcept(
+ __all<is_nothrow_move_constructible_v<_Types>...>::value)
+ : __move_constructor(__valueless_t{}) {
+ this->__generic_construct(*this, _VSTD::move(__that));
+ });
+
+_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
+ _Trait::_Unavailable,
+ __move_constructor(__move_constructor&&) = delete;);
+
+#undef _LIBCPP_VARIANT_MOVE_CONSTRUCTOR
+
+template <class _Traits, _Trait = _Traits::__copy_constructible_trait>
+class _LIBCPP_TYPE_VIS_ONLY __copy_constructor;
+
+#define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, \
+ copy_constructor) \
+ template <class... _Types> \
+ class _LIBCPP_TYPE_VIS_ONLY __copy_constructor<__traits<_Types...>, \
+ copy_constructible_trait> \
+ : public __move_constructor<__traits<_Types...>> { \
+ using __base_type = __move_constructor<__traits<_Types...>>; \
+ \
+ public: \
+ using __base_type::__base_type; \
+ using __base_type::operator=; \
+ \
+ copy_constructor \
+ __copy_constructor(__copy_constructor&&) = default; \
+ ~__copy_constructor() = default; \
+ __copy_constructor& operator=(const __copy_constructor&) = default; \
+ __copy_constructor& operator=(__copy_constructor&&) = default; \
+ }
+
+_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
+ _Trait::_TriviallyAvailable,
+ __copy_constructor(const __copy_constructor& __that) = default;);
+
+_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
+ _Trait::_Available,
+ __copy_constructor(const __copy_constructor& __that)
+ : __copy_constructor(__valueless_t{}) {
+ this->__generic_construct(*this, __that);
+ });
+
+_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
+ _Trait::_Unavailable,
+ __copy_constructor(const __copy_constructor&) = delete;);
+
+#undef _LIBCPP_VARIANT_COPY_CONSTRUCTOR
+
+template <class _Traits>
+class _LIBCPP_TYPE_VIS_ONLY __assignment : public __copy_constructor<_Traits> {
+ using __base_type = __copy_constructor<_Traits>;
+
+public:
+ using __base_type::__base_type;
+ using __base_type::operator=;
+
+ template <size_t _Ip, class... _Args>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void __emplace(_Args&&... __args) {
+ this->__destroy();
+ this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
+ _VSTD::forward<_Args>(__args)...);
+ this->__index = _Ip;
+ }
+
+protected:
+ template <bool _CopyAssign, size_t _Ip, class _Tp, class _Arg>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void __assign_alt(__alt<_Ip, _Tp>& __a,
+ _Arg&& __arg,
+ bool_constant<_CopyAssign> __tag) {
+ if (this->index() == _Ip) {
+ __a.__value = _VSTD::forward<_Arg>(__arg);
+ } else {
+ struct {
+ void operator()(true_type) const {
+ __this->__emplace<_Ip>(_Tp(_VSTD::forward<_Arg>(__arg)));
+ }
+ void operator()(false_type) const {
+ __this->__emplace<_Ip>(_VSTD::forward<_Arg>(__arg));
+ }
+ __assignment* __this;
+ _Arg&& __arg;
+ } __impl{this, _VSTD::forward<_Arg>(__arg)};
+ __impl(__tag);
+ }
+ }
+
+ template <class _That>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void __generic_assign(_That&& __that) {
+ if (this->valueless_by_exception() && __that.valueless_by_exception()) {
+ // do nothing.
+ } else if (__that.valueless_by_exception()) {
+ this->__destroy();
+ } else {
+ __visitation::__base::__visit_alt_at(
+ __that.index(),
+ [this](auto& __this_alt, auto&& __that_alt) {
+ this->__assign_alt(
+ __this_alt,
+ _VSTD::forward<decltype(__that_alt)>(__that_alt).__value,
+ is_lvalue_reference<_That>{});
+ },
+ *this, _VSTD::forward<_That>(__that));
+ }
+ }
+};
+
+template <class _Traits, _Trait = _Traits::__move_assignable_trait>
+class _LIBCPP_TYPE_VIS_ONLY __move_assignment;
+
+#define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, \
+ move_assignment) \
+ template <class... _Types> \
+ class _LIBCPP_TYPE_VIS_ONLY __move_assignment<__traits<_Types...>, \
+ move_assignable_trait> \
+ : public __assignment<__traits<_Types...>> { \
+ using __base_type = __assignment<__traits<_Types...>>; \
+ \
+ public: \
+ using __base_type::__base_type; \
+ using __base_type::operator=; \
+ \
+ __move_assignment(const __move_assignment&) = default; \
+ __move_assignment(__move_assignment&&) = default; \
+ ~__move_assignment() = default; \
+ __move_assignment& operator=(const __move_assignment&) = default; \
+ move_assignment \
+ }
+
+_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
+ _Trait::_TriviallyAvailable,
+ __move_assignment& operator=(__move_assignment&& __that) = default;);
+
+_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
+ _Trait::_Available,
+ __move_assignment& operator=(__move_assignment&& __that) noexcept(
+ __all<(is_nothrow_move_constructible_v<_Types> &&
+ is_nothrow_move_assignable_v<_Types>)...>::value) {
+ this->__generic_assign(_VSTD::move(__that));
+ return *this;
+ });
+
+_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
+ _Trait::_Unavailable,
+ __move_assignment& operator=(__move_assignment&&) = delete;);
+
+#undef _LIBCPP_VARIANT_MOVE_ASSIGNMENT
+
+template <class _Traits, _Trait = _Traits::__copy_assignable_trait>
+class _LIBCPP_TYPE_VIS_ONLY __copy_assignment;
+
+#define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, \
+ copy_assignment) \
+ template <class... _Types> \
+ class _LIBCPP_TYPE_VIS_ONLY __copy_assignment<__traits<_Types...>, \
+ copy_assignable_trait> \
+ : public __move_assignment<__traits<_Types...>> { \
+ using __base_type = __move_assignment<__traits<_Types...>>; \
+ \
+ public: \
+ using __base_type::__base_type; \
+ using __base_type::operator=; \
+ \
+ __copy_assignment(const __copy_assignment&) = default; \
+ __copy_assignment(__copy_assignment&&) = default; \
+ ~__copy_assignment() = default; \
+ copy_assignment \
+ __copy_assignment& operator=(__copy_assignment&&) = default; \
+ }
+
+_LIBCPP_VARIANT_COPY_ASSIGNMENT(
+ _Trait::_TriviallyAvailable,
+ __copy_assignment& operator=(const __copy_assignment& __that) = default;);
+
+_LIBCPP_VARIANT_COPY_ASSIGNMENT(
+ _Trait::_Available,
+ __copy_assignment& operator=(const __copy_assignment& __that) {
+ this->__generic_assign(__that);
+ return *this;
+ });
+
+_LIBCPP_VARIANT_COPY_ASSIGNMENT(
+ _Trait::_Unavailable,
+ __copy_assignment& operator=(const __copy_assignment&) = delete;);
+
+#undef _LIBCPP_VARIANT_COPY_ASSIGNMENT
+
+template <class... _Types>
+class _LIBCPP_TYPE_VIS_ONLY __impl
+ : public __copy_assignment<__traits<_Types...>> {
+ using __base_type = __copy_assignment<__traits<_Types...>>;
+
+public:
+ using __base_type::__base_type;
+ using __base_type::operator=;
+
+ template <size_t _Ip, class _Arg>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void __assign(_Arg&& __arg) {
+ this->__assign_alt(__access::__base::__get_alt<_Ip>(*this),
+ _VSTD::forward<_Arg>(__arg),
+ false_type{});
+ }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ void __swap(__impl& __that) {
+ if (this->valueless_by_exception() && __that.valueless_by_exception()) {
+ // do nothing.
+ } else if (this->index() == __that.index()) {
+ __visitation::__base::__visit_alt_at(
+ this->index(),
+ [](auto& __this_alt, auto& __that_alt) {
+ using _VSTD::swap;
+ swap(__this_alt.__value, __that_alt.__value);
+ },
+ *this,
+ __that);
+ } else {
+ __impl* __lhs = this;
+ __impl* __rhs = _VSTD::addressof(__that);
+ if (__lhs->__move_nothrow() && !__rhs->__move_nothrow()) {
+ _VSTD::swap(__lhs, __rhs);
+ }
+ __impl __tmp(_VSTD::move(*__rhs));
+#ifndef _LIBCPP_NO_EXCEPTIONS
+ // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
+ // and `__tmp` is nothrow move constructible then we move `__tmp` back
+ // into `__rhs` and provide the strong exception safety guarentee.
+ try {
+ this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
+ } catch (...) {
+ if (__tmp.__move_nothrow()) {
+ this->__generic_construct(*__rhs, _VSTD::move(__tmp));
+ }
+ throw;
+ }
+#else
+ this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
+#endif
+ this->__generic_construct(*__lhs, _VSTD::move(__tmp));
+ }
+ }
+
+private:
+ inline _LIBCPP_INLINE_VISIBILITY
+ bool __move_nothrow() const {
+ constexpr bool __results[] = {is_nothrow_move_constructible_v<_Types>...};
+ return this->valueless_by_exception() || __results[this->index()];
+ }
+};
+
+template <class... _Types>
+struct __overload;
+
+template <>
+struct __overload<> { void operator()() const; };
+
+template <class _Tp, class... _Types>
+struct __overload<_Tp, _Types...> : __overload<_Types...> {
+ using __overload<_Types...>::operator();
+ __identity<_Tp> operator()(_Tp) const;
+};
+
+template <class _Tp, class... _Types>
+using __best_match_t = typename result_of_t<__overload<_Types...>(_Tp&&)>::type;
+
+} // __variant_detail
+
+template <class... _Types>
+class _LIBCPP_TYPE_VIS_ONLY variant
+ : private __sfinae_ctor_base<
+ __all<is_copy_constructible_v<_Types>...>::value,
+ __all<is_move_constructible_v<_Types>...>::value>,
+ private __sfinae_assign_base<
+ __all<(is_copy_constructible_v<_Types> &&
+ is_move_constructible_v<_Types> &&
+ is_copy_assignable_v<_Types>)...>::value,
+ __all<(is_move_constructible_v<_Types> &&
+ is_move_assignable_v<_Types>)...>::value> {
+ static_assert(0 < sizeof...(_Types),
+ "variant must consist of at least one alternative.");
+
+ static_assert(__all<!is_array_v<_Types>...>::value,
+ "variant can not have an array type as an alternative.");
+
+ static_assert(__all<!is_reference_v<_Types>...>::value,
+ "variant can not have a reference type as an alternative.");
+
+ static_assert(__all<!is_void_v<_Types>...>::value,
+ "variant can not have a void type as an alternative.");
+
+ using __first_type = variant_alternative_t<0, variant>;
+
+public:
+ template <bool _Dummy = true,
+ enable_if_t<__dependent_type<is_default_constructible<__first_type>,
+ _Dummy>::value,
+ int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr variant() noexcept(is_nothrow_default_constructible_v<__first_type>)
+ : __impl(in_place_index<0>) {}
+
+ variant(const variant&) = default;
+ variant(variant&&) = default;
+
+ template <
+ class _Arg,
+ enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0,
+ class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
+ size_t _Ip =
+ __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+ enable_if_t<is_constructible_v<_Tp, _Arg>, int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr variant(_Arg&& __arg) noexcept(
+ is_nothrow_constructible_v<_Tp, _Arg>)
+ : __impl(in_place_index<_Ip>, _VSTD::forward<_Arg>(__arg)) {}
+
+ template <size_t _Ip, class... _Args,
+ enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
+ class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+ enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ explicit constexpr variant(
+ in_place_index_t<_Ip>,
+ _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
+ : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
+
+ template <
+ size_t _Ip,
+ class _Up,
+ class... _Args,
+ enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
+ class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+ enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+ int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ explicit constexpr variant(
+ in_place_index_t<_Ip>,
+ initializer_list<_Up> __il,
+ _Args&&... __args) noexcept(
+ is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
+ : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
+
+ template <
+ class _Tp,
+ class... _Args,
+ size_t _Ip =
+ __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+ enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ explicit constexpr variant(in_place_type_t<_Tp>, _Args&&... __args) noexcept(
+ is_nothrow_constructible_v<_Tp, _Args...>)
+ : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
+
+ template <
+ class _Tp,
+ class _Up,
+ class... _Args,
+ size_t _Ip =
+ __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+ enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+ int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ explicit constexpr variant(
+ in_place_type_t<_Tp>,
+ initializer_list<_Up> __il,
+ _Args&&... __args) noexcept(
+ is_nothrow_constructible_v<_Tp, initializer_list< _Up>&, _Args...>)
+ : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
+
+ ~variant() = default;
+
+ variant& operator=(const variant&) = default;
+ variant& operator=(variant&&) = default;
+
+ template <
+ class _Arg,
+ enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0,
+ class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
+ size_t _Ip =
+ __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+ enable_if_t<is_assignable_v<_Tp&, _Arg> && is_constructible_v<_Tp, _Arg>,
+ int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ variant& operator=(_Arg&& __arg) noexcept(
+ is_nothrow_assignable_v<_Tp&, _Arg> &&
+ is_nothrow_constructible_v<_Tp, _Arg>) {
+ __impl.template __assign<_Ip>(_VSTD::forward<_Arg>(__arg));
+ return *this;
+ }
+
+ template <
+ size_t _Ip,
+ class... _Args,
+ enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
+ class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+ enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void emplace(_Args&&... __args) {
+ __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
+ }
+
+ template <
+ size_t _Ip,
+ class _Up,
+ class... _Args,
+ enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
+ class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+ enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+ int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void emplace(initializer_list<_Up> __il, _Args&&... __args) {
+ __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
+ }
+
+ template <
+ class _Tp,
+ class... _Args,
+ size_t _Ip =
+ __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+ enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void emplace(_Args&&... __args) {
+ __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
+ }
+
+ template <
+ class _Tp,
+ class _Up,
+ class... _Args,
+ size_t _Ip =
+ __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+ enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+ int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void emplace(initializer_list<_Up> __il, _Args&&... __args) {
+ __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
+ }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr bool valueless_by_exception() const noexcept {
+ return __impl.valueless_by_exception();
+ }
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ constexpr size_t index() const noexcept { return __impl.index(); }
+
+ template <
+ bool _Dummy = true,
+ enable_if_t<
+ __all<(
+ __dependent_type<is_move_constructible<_Types>, _Dummy>::value &&
+ __dependent_type<is_swappable<_Types>, _Dummy>::value)...>::value,
+ int> = 0>
+ inline _LIBCPP_INLINE_VISIBILITY
+ void swap(variant& __that) noexcept(
+ __all<(is_nothrow_move_constructible_v<_Types> &&
+ is_nothrow_swappable_v<_Types>)...>::value) {
+ __impl.__swap(__that.__impl);
+ }
+
+private:
+ __variant_detail::__impl<_Types...> __impl;
+
+ friend struct __variant_detail::__access::__variant;
+ friend struct __variant_detail::__visitation::__variant;
+};
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool __holds_alternative(const variant<_Types...>& __v) noexcept {
+ return __v.index() == _Ip;
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept {
+ return __holds_alternative<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <size_t _Ip, class _Vp>
+inline _LIBCPP_INLINE_VISIBILITY
+static constexpr auto&& __generic_get(_Vp&& __v) {
+ using __variant_detail::__access::__variant;
+ if (!__holds_alternative<_Ip>(__v)) {
+ throw bad_variant_access{};
+ }
+ return __variant::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v)).__value;
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr variant_alternative_t<_Ip, variant<_Types...>>& get(
+ variant<_Types...>& __v) {
+ static_assert(_Ip < sizeof...(_Types));
+ static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+ return __generic_get<_Ip>(__v);
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr variant_alternative_t<_Ip, variant<_Types...>>&& get(
+ variant<_Types...>&& __v) {
+ static_assert(_Ip < sizeof...(_Types));
+ static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+ return __generic_get<_Ip>(_VSTD::move(__v));
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const variant_alternative_t<_Ip, variant<_Types...>>& get(
+ const variant<_Types...>& __v) {
+ static_assert(_Ip < sizeof...(_Types));
+ static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+ return __generic_get<_Ip>(__v);
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const variant_alternative_t<_Ip, variant<_Types...>>&& get(
+ const variant<_Types...>&& __v) {
+ static_assert(_Ip < sizeof...(_Types));
+ static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+ return __generic_get<_Ip>(_VSTD::move(__v));
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp& get(variant<_Types...>& __v) {
+ static_assert(!is_void_v<_Tp>);
+ return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp&& get(variant<_Types...>&& __v) {
+ static_assert(!is_void_v<_Tp>);
+ return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
+ _VSTD::move(__v));
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const _Tp& get(const variant<_Types...>& __v) {
+ static_assert(!is_void_v<_Tp>);
+ return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const _Tp&& get(const variant<_Types...>&& __v) {
+ static_assert(!is_void_v<_Tp>);
+ return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
+ _VSTD::move(__v));
+}
+
+template <size_t _Ip, class _Vp>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr auto* __generic_get_if(_Vp* __v) noexcept {
+ using __variant_detail::__access::__variant;
+ return __v && __holds_alternative<_Ip>(*__v)
+ ? _VSTD::addressof(__variant::__get_alt<_Ip>(*__v).__value)
+ : nullptr;
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<variant_alternative_t<_Ip, variant<_Types...>>>
+get_if(variant<_Types...>* __v) noexcept {
+ static_assert(_Ip < sizeof...(_Types));
+ static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+ return __generic_get_if<_Ip>(__v);
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<const variant_alternative_t<_Ip, variant<_Types...>>>
+get_if(const variant<_Types...>* __v) noexcept {
+ static_assert(_Ip < sizeof...(_Types));
+ static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+ return __generic_get_if<_Ip>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<_Tp>
+get_if(variant<_Types...>* __v) noexcept {
+ static_assert(!is_void_v<_Tp>);
+ return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<const _Tp>
+get_if(const variant<_Types...>* __v) noexcept {
+ static_assert(!is_void_v<_Tp>);
+ return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator==(const variant<_Types...>& __lhs,
+ const variant<_Types...>& __rhs) {
+ using __variant_detail::__visitation::__variant;
+ if (__lhs.index() != __rhs.index()) return false;
+ if (__lhs.valueless_by_exception()) return true;
+ return __variant::__visit_value_at(__lhs.index(), equal_to<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator!=(const variant<_Types...>& __lhs,
+ const variant<_Types...>& __rhs) {
+ using __variant_detail::__visitation::__variant;
+ if (__lhs.index() != __rhs.index()) return true;
+ if (__lhs.valueless_by_exception()) return false;
+ return __variant::__visit_value_at(
+ __lhs.index(), not_equal_to<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<(const variant<_Types...>& __lhs,
+ const variant<_Types...>& __rhs) {
+ using __variant_detail::__visitation::__variant;
+ if (__rhs.valueless_by_exception()) return false;
+ if (__lhs.valueless_by_exception()) return true;
+ if (__lhs.index() < __rhs.index()) return true;
+ if (__lhs.index() > __rhs.index()) return false;
+ return __variant::__visit_value_at(__lhs.index(), less<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>(const variant<_Types...>& __lhs,
+ const variant<_Types...>& __rhs) {
+ using __variant_detail::__visitation::__variant;
+ if (__lhs.valueless_by_exception()) return false;
+ if (__rhs.valueless_by_exception()) return true;
+ if (__lhs.index() > __rhs.index()) return true;
+ if (__lhs.index() < __rhs.index()) return false;
+ return __variant::__visit_value_at(__lhs.index(), greater<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<=(const variant<_Types...>& __lhs,
+ const variant<_Types...>& __rhs) {
+ using __variant_detail::__visitation::__variant;
+ if (__lhs.valueless_by_exception()) return true;
+ if (__rhs.valueless_by_exception()) return false;
+ if (__lhs.index() < __rhs.index()) return true;
+ if (__lhs.index() > __rhs.index()) return false;
+ return __variant::__visit_value_at(
+ __lhs.index(), less_equal<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>=(const variant<_Types...>& __lhs,
+ const variant<_Types...>& __rhs) {
+ using __variant_detail::__visitation::__variant;
+ if (__rhs.valueless_by_exception()) return true;
+ if (__lhs.valueless_by_exception()) return false;
+ if (__lhs.index() > __rhs.index()) return true;
+ if (__lhs.index() < __rhs.index()) return false;
+ return __variant::__visit_value_at(
+ __lhs.index(), greater_equal<>{}, __lhs, __rhs);
+}
+
+template <class _Visitor, class... _Vs>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
+ using __variant_detail::__visitation::__variant;
+ bool __results[] = {__vs.valueless_by_exception()...};
+ for (bool __result : __results) {
+ if (__result) {
+ throw bad_variant_access{};
+ }
+ }
+ return __variant::__visit_value(_VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs)...);
+}
+
+struct _LIBCPP_TYPE_VIS_ONLY monostate {};
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<(monostate, monostate) noexcept { return false; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>(monostate, monostate) noexcept { return false; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<=(monostate, monostate) noexcept { return true; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>=(monostate, monostate) noexcept { return true; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator==(monostate, monostate) noexcept { return true; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator!=(monostate, monostate) noexcept { return false; }
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+auto swap(variant<_Types...>& __lhs,
+ variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs)))
+ -> decltype(__lhs.swap(__rhs)) {
+ __lhs.swap(__rhs);
+}
+
+template <class... _Types>
+struct _LIBCPP_TYPE_VIS_ONLY hash<variant<_Types...>> {
+ using argument_type = variant<_Types...>;
+ using result_type = size_t;
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ result_type operator()(const argument_type& __v) const {
+ using __variant_detail::__visitation::__variant;
+ return __v.valueless_by_exception()
+ ? __v.index()
+ : __variant::__visit_alt(
+ [](const auto& __alt) {
+ using __alt_type = decay_t<decltype(__alt)>;
+ using __value_type = typename __alt_type::__value_type;
+ return hash<__value_type>{}(__alt.__value);
+ },
+ __v);
+ }
+};
+
+template <>
+struct _LIBCPP_TYPE_VIS_ONLY hash<monostate> {
+ using argument_type = monostate;
+ using result_type = size_t;
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ result_type operator()(const argument_type&) const { return 0; }
+};
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_VARIANT
