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llvm-project/libcxx/include/variant
Louis Dionne 2eadbc8614 [libc++] Rework the whole availability markup implementation 
Currently, vendor-specific availability markup is enabled by default.
This means that even when building against trunk libc++, the headers
will by default prevent you from using some features that were not
released in the dylib on your target platform. This is a source of
frustration since people building libc++ from sources are usually not
trying to use some vendor's released dylib.

For that reason, I've been thinking for a long time that availability
annotations should be off by default, which is the primary change that
this commit enables.

In addition, it reworks the implementation to make it easier for new
vendors to add availability annotations for their platform, and it
refreshes the documentation to reflect the current state of the codebase.

Finally, a CMake configuration option is added to control whether
availability annotations should be turned on for the flavor of libc++
being created. The intent is for vendors like Apple to turn it on, and
for the upstream libc++ to leave it off (the default).

Differential Revision: https://reviews.llvm.org/D90843
2020-11-05 12:28:52 -05:00

1760 lines
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// -*- C++ -*-
//===------------------------------ variant -------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#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&); // constexpr in C++20
variant(variant&&) noexcept(see below); // constexpr in C++20
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&); // constexpr in C++20
variant& operator=(variant&&) noexcept(see below); // constexpr in C++20
template <class T> variant& operator=(T&&) noexcept(see below);
// 20.7.2.4, modifiers
template <class T, class... Args>
T& emplace(Args&&...);
template <class T, class U, class... Args>
T& emplace(initializer_list<U>, Args&&...);
template <size_t I, class... Args>
variant_alternative_t<I, variant>& emplace(Args&&...);
template <size_t I, class U, class... Args>
variant_alternative_t<I, variant>& 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>
inline 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...>>;
inline 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 <__availability>
#include <__tuple>
#include <array>
#include <exception>
#include <functional>
#include <initializer_list>
#include <new>
#include <tuple>
#include <type_traits>
#include <utility>
#include <limits>
#include <version>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
namespace std { // explicitly not using versioning namespace
class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS bad_variant_access : public exception {
public:
virtual const char* what() const _NOEXCEPT;
};
} // namespace std
_LIBCPP_BEGIN_NAMESPACE_STD
// TODO: GCC 5 lies about its support for C++17 (it says it supports it but it
// really doesn't). That breaks variant, which uses some C++17 features.
// Remove this once we drop support for GCC 5.
#if _LIBCPP_STD_VER > 14 && !(defined(_LIBCPP_COMPILER_GCC) && _GNUC_VER_NEW < 6000)
_LIBCPP_NORETURN
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
void __throw_bad_variant_access() {
#ifndef _LIBCPP_NO_EXCEPTIONS
throw bad_variant_access();
#else
_VSTD::abort();
#endif
}
template <class... _Types>
class _LIBCPP_TEMPLATE_VIS variant;
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_size;
template <class _Tp>
_LIBCPP_INLINE_VAR constexpr size_t variant_size_v = variant_size<_Tp>::value;
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_size<const _Tp> : variant_size<_Tp> {};
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_size<volatile _Tp> : variant_size<_Tp> {};
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_size<const volatile _Tp>
: variant_size<_Tp> {};
template <class... _Types>
struct _LIBCPP_TEMPLATE_VIS variant_size<variant<_Types...>>
: integral_constant<size_t, sizeof...(_Types)> {};
template <size_t _Ip, class _Tp>
struct _LIBCPP_TEMPLATE_VIS 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_TEMPLATE_VIS variant_alternative<_Ip, const _Tp>
: add_const<variant_alternative_t<_Ip, _Tp>> {};
template <size_t _Ip, class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, volatile _Tp>
: add_volatile<variant_alternative_t<_Ip, _Tp>> {};
template <size_t _Ip, class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const volatile _Tp>
: add_cv<variant_alternative_t<_Ip, _Tp>> {};
template <size_t _Ip, class... _Types>
struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, variant<_Types...>> {
static_assert(_Ip < sizeof...(_Types), "Index out of bounds in std::variant_alternative<>");
using type = __type_pack_element<_Ip, _Types...>;
};
_LIBCPP_INLINE_VAR constexpr size_t variant_npos = static_cast<size_t>(-1);
constexpr int __choose_index_type(unsigned int __num_elem) {
if (__num_elem < std::numeric_limits<unsigned char>::max())
return 0;
if (__num_elem < std::numeric_limits<unsigned short>::max())
return 1;
return 2;
}
template <size_t _NumAlts>
using __variant_index_t =
#ifndef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
unsigned int;
#else
std::tuple_element_t<
__choose_index_type(_NumAlts),
std::tuple<unsigned char, unsigned short, unsigned int>
>;
#endif
template <class _IndexType>
constexpr _IndexType __variant_npos = static_cast<_IndexType>(-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 <class _Tp,
template <class> class _IsTriviallyAvailable,
template <class> 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 <class... _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,
__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 {
#define _LIBCPP_VARIANT_CASES_4(_Case, _Base) \
_Case(_Base + 0) \
_Case(_Base + 1) \
_Case(_Base + 2) \
_Case(_Base + 3)
#define _LIBCPP_VARIANT_CASES_16(_Case, _Base) \
_LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 0) \
_LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 1) \
_LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 2) \
_LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 3)
#define _LIBCPP_VARIANT_CASES_64(_Case, _Base) \
_LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 0) \
_LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 1) \
_LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 2) \
_LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 3)
#define _LIBCPP_VARIANT_CASES_256(_Case, _Base) \
_LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 0) \
_LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 1) \
_LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 2) \
_LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 3)
#define _LIBCPP_VARIANT_CASES(_NumCases, _Case) \
_LIBCPP_CONCAT(_LIBCPP_VARIANT_CASES_, _NumCases)(_Case, 0)
#define _LIBCPP_VARIANT_SWITCH_MAX 256
template <class _Iter, class _Fp, size_t... _Is>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr void __fill_cartesian_impl(
_Iter __iter, _Fp __f, index_sequence<_Is...>) {
*__iter = __f(integral_constant<size_t, _Is>{}...);
}
template <class _Iter, class _Fp, size_t... _Is, size_t... _Js, class... _Ls>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr void __fill_cartesian_impl(
_Iter __iter, _Fp __f, index_sequence<_Is...>, index_sequence<_Js...>, _Ls... __ls) {
constexpr size_t _Mp = (1 * ... * _Ls::size());
(__fill_cartesian_impl(
__iter + _Js * _Mp, __f, index_sequence<_Is..., _Js>{}, __ls...), ...);
}
template <size_t... _Ns, class _Iter, class _Fp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr void __fill_cartesian(_Iter __iter, _Fp __f) {
__fill_cartesian_impl(
__iter, __f, index_sequence<>{}, make_index_sequence<_Ns>{}...);
}
template <size_t _Np, size_t... _Ns>
struct __multi {
inline _LIBCPP_INLINE_VISIBILITY
static constexpr size_t __size = (_Np * ... * _Ns);
inline _LIBCPP_INLINE_VISIBILITY
static constexpr size_t
__index(const size_t (&__is)[sizeof...(_Ns) + 1]) noexcept {
constexpr size_t __ns[] = {_Ns..., 1};
size_t __result = 0;
for (size_t __i = 0; __i < sizeof...(_Ns) + 1; ++__i) {
if (__is[__i] == variant_npos) {
return variant_npos;
}
__result += __is[__i];
__result *= __ns[__i];
}
return __result;
}
};
template <size_t... _Ns>
struct __indices {
inline _LIBCPP_INLINE_VISIBILITY
static constexpr auto __value = [] {
using _Tp = array<size_t, sizeof...(_Ns)>;
array<_Tp, (1 * ... * _Ns)> __result = {};
__fill_cartesian<_Ns...>(__result.begin(),
[](auto... __is) -> _Tp { return {__is...}; });
return __result;
}();
};
template <size_t... _Ns, class _Fp, class _Rp, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr auto __make_vtable_impl(_Fp __f, _Rp (*)(_Args...)) {
array<_Rp (*)(_Args...), (1 * ... * _Ns) + 1> __result = {
[](_Args...) -> _Rp { __throw_bad_variant_access(); }
};
__fill_cartesian<_Ns...>(__result.begin() + 1, __f);
return __result;
}
template <size_t... _Ns, class _Fp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr auto __make_vtable(_Fp __f) {
using _Tp = decltype(__f(integral_constant<size_t, (_Ns, 0)>{}...));
return __make_vtable_impl<_Ns...>(__f, _Tp{});
}
struct __base {
template <class _Vis, class... _Vs>
struct __dispatch {
template <size_t... _Is>
inline _LIBCPP_INLINE_VISIBILITY
constexpr auto operator()(integral_constant<size_t, _Is>...) const noexcept {
return +[](_Vis&& __vis, _Vs&&... __vs) -> decltype(auto) {
return __invoke_constexpr(
_VSTD::forward<_Vis>(__vis),
__access::__base::__get_alt<_Is>(_VSTD::forward<_Vs>(__vs))...);
};
}
};
template <class _Vis, class _Vp, class _Wp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
__visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
constexpr size_t __size = __uncvref_t<_Vp>::__size();
static_assert(__size == __uncvref_t<_Wp>::__size());
constexpr auto __dispatch_at = [](auto __i) {
return __dispatch<_Vis, _Vp, _Wp>{}(__i, __i);
};
#define _LIBCPP_VARIANT_CASE(_Ip) \
case _Ip: { \
if constexpr (_Ip < __size) { \
return __dispatch_at(integral_constant<size_t, _Ip>{})( \
_VSTD::forward<_Vis>(__vis), \
_VSTD::forward<_Vp>(__v), \
_VSTD::forward<_Wp>(__w)); \
} else { \
_LIBCPP_UNREACHABLE(); \
} \
}
if constexpr (__size <= _LIBCPP_VARIANT_SWITCH_MAX) {
switch (__index) {
_LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE)
default: __throw_bad_variant_access();
}
} else {
constexpr auto __vtable = __make_vtable<__size>(__dispatch_at);
return __vtable[__index + 1](_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Vp>(__v),
_VSTD::forward<_Wp>(__w));
}
#undef _LIBCPP_VARIANT_CASE
}
template <size_t... _Is, class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) {
if constexpr (sizeof...(_Vs) == 0) {
return __invoke_constexpr(_VSTD::forward<_Vis>(__vis));
} else {
return __visit_alt_impl(index_sequence_for<_Vs...>{},
_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Vs>(__vs)...);
}
}
template <size_t... _Is, class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
__visit_alt_impl(index_sequence<_Is...>, _Vis&& __vis, _Vs&&... __vs) {
using __multi = __multi<__uncvref_t<_Vs>::__size()...>;
constexpr __dispatch<_Vis, _Vs...> __dispatch;
#define _LIBCPP_VARIANT_CASE(_Ip) \
case _Ip: { \
if constexpr (_Ip < __multi::__size) { \
return __dispatch(integral_constant<size_t, __itable[_Ip][_Is]>{}...)( \
_VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...); \
} else { \
_LIBCPP_UNREACHABLE(); \
} \
}
if constexpr (__multi::__size <= _LIBCPP_VARIANT_SWITCH_MAX) {
constexpr const auto& __itable =
__indices<__uncvref_t<_Vs>::__size()...>::__value;
switch (__multi::__index({__vs.index()...})) {
_LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE)
default: __throw_bad_variant_access();
}
} else {
constexpr auto __vtable =
__make_vtable<__uncvref_t<_Vs>::__size()...>(__dispatch);
return __vtable[__multi::__index({__vs.index()...}) + 1](
_VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...);
}
#undef _LIBCPP_VARIANT_CASE
}
};
struct __variant {
template <class _Vis, class _Vp, class _Wp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
__visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
return __base::__visit_alt_at(__index,
_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Vp>(__v).__impl,
_VSTD::forward<_Wp>(__w).__impl);
}
template <class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) {
return __base::__visit_alt(_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Vs>(__vs).__impl...);
}
template <class _Vis, class _Vp, class _Wp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
__visit_value_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
return __visit_alt_at(__index,
__make_value_visitor(_VSTD::forward<_Vis>(__vis)),
_VSTD::forward<_Vp>(__v),
_VSTD::forward<_Wp>(__w));
}
template <class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto) __visit_value(_Vis&& __vis, _Vs&&... __vs) {
return __visit_alt(__make_value_visitor(_VSTD::forward<_Vis>(__vis)),
_VSTD::forward<_Vs>(__vs)...);
}
private:
template <class _Vis, class... _Values>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr void __std_visit_exhaustive_visitor_check() {
static_assert(is_invocable_v<_Vis, _Values...>,
"`std::visit` requires the visitor to be exhaustive.");
}
template <class _Vis>
struct __value_visitor {
template <class... _Alts>
inline _LIBCPP_INLINE_VISIBILITY
constexpr decltype(auto) operator()(_Alts&&... __alts) const {
__std_visit_exhaustive_visitor_check<
_Vis, decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
return __invoke_constexpr(_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Alts>(__alts).__value...);
}
_Vis&& __vis;
};
template <class _Vis>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr auto __make_value_visitor(_Vis&& __vis) {
return __value_visitor<_Vis>{_VSTD::forward<_Vis>(__vis)};
}
};
#undef _LIBCPP_VARIANT_SWITCH_MAX
#undef _LIBCPP_VARIANT_CASES
#undef _LIBCPP_VARIANT_CASES_256
#undef _LIBCPP_VARIANT_CASES_64
#undef _LIBCPP_VARIANT_CASES_16
#undef _LIBCPP_VARIANT_CASES_4
} // namespace __visitation
template <size_t _Index, class _Tp>
struct _LIBCPP_TEMPLATE_VIS __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_TEMPLATE_VIS __union;
template <_Trait _DestructibleTrait, size_t _Index>
union _LIBCPP_TEMPLATE_VIS __union<_DestructibleTrait, _Index> {};
#define _LIBCPP_VARIANT_UNION(destructible_trait, destructor) \
template <size_t _Index, class _Tp, class... _Types> \
union _LIBCPP_TEMPLATE_VIS __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_TEMPLATE_VIS __base {
public:
using __index_t = __variant_index_t<sizeof...(_Types)>;
inline _LIBCPP_INLINE_VISIBILITY
explicit constexpr __base(__valueless_t tag) noexcept
: __data(tag), __index(__variant_npos<__index_t>) {}
template <size_t _Ip, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
explicit constexpr __base(in_place_index_t<_Ip>, _Args&&... __args)
:
__data(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...),
__index(_Ip) {}
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<__index_t> ? 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;
__index_t __index;
friend struct __access::__base;
friend struct __visitation::__base;
};
template <class _Traits, _Trait = _Traits::__destructible_trait>
class _LIBCPP_TEMPLATE_VIS __dtor;
#define _LIBCPP_VARIANT_DESTRUCTOR(destructible_trait, destructor, destroy) \
template <class... _Types> \
class _LIBCPP_TEMPLATE_VIS __dtor<__traits<_Types...>, \
destructible_trait> \
: public __base<destructible_trait, _Types...> { \
using __base_type = __base<destructible_trait, _Types...>; \
using __index_t = typename __base_type::__index_t; \
\
public: \
using __base_type::__base_type; \
using __base_type::operator=; \
\
__dtor(const __dtor&) = default; \
__dtor(__dtor&&) = default; \
destructor \
__dtor& operator=(const __dtor&) = default; \
__dtor& operator=(__dtor&&) = default; \
\
protected: \
inline _LIBCPP_INLINE_VISIBILITY \
destroy \
}
_LIBCPP_VARIANT_DESTRUCTOR(
_Trait::_TriviallyAvailable,
~__dtor() = default;,
void __destroy() noexcept { this->__index = __variant_npos<__index_t>; });
_LIBCPP_VARIANT_DESTRUCTOR(
_Trait::_Available,
~__dtor() { __destroy(); },
void __destroy() noexcept {
if (!this->valueless_by_exception()) {
__visitation::__base::__visit_alt(
[](auto& __alt) noexcept {
using __alt_type = __uncvref_t<decltype(__alt)>;
__alt.~__alt_type();
},
*this);
}
this->__index = __variant_npos<__index_t>;
});
_LIBCPP_VARIANT_DESTRUCTOR(
_Trait::_Unavailable,
~__dtor() = delete;,
void __destroy() noexcept = delete;);
#undef _LIBCPP_VARIANT_DESTRUCTOR
template <class _Traits>
class _LIBCPP_TEMPLATE_VIS __ctor : public __dtor<_Traits> {
using __base_type = __dtor<_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 _Tp& __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) {
auto* __result = ::new ((void*)_VSTD::addressof(__a))
__alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
return __result->__value;
}
template <class _Rhs>
inline _LIBCPP_INLINE_VISIBILITY
static void __generic_construct(__ctor& __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_TEMPLATE_VIS __move_constructor;
#define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, \
move_constructor) \
template <class... _Types> \
class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \
move_constructible_trait> \
: public __ctor<__traits<_Types...>> { \
using __base_type = __ctor<__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_TEMPLATE_VIS __copy_constructor;
#define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, \
copy_constructor) \
template <class... _Types> \
class _LIBCPP_TEMPLATE_VIS __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_TEMPLATE_VIS __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
auto& __emplace(_Args&&... __args) {
this->__destroy();
auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
_VSTD::forward<_Args>(__args)...);
this->__index = _Ip;
return __res;
}
protected:
template <size_t _Ip, class _Tp, class _Arg>
inline _LIBCPP_INLINE_VISIBILITY
void __assign_alt(__alt<_Ip, _Tp>& __a, _Arg&& __arg) {
if (this->index() == _Ip) {
__a.__value = _VSTD::forward<_Arg>(__arg);
} else {
struct {
void operator()(true_type) const {
__this->__emplace<_Ip>(_VSTD::forward<_Arg>(__arg));
}
void operator()(false_type) const {
__this->__emplace<_Ip>(_Tp(_VSTD::forward<_Arg>(__arg)));
}
__assignment* __this;
_Arg&& __arg;
} __impl{this, _VSTD::forward<_Arg>(__arg)};
__impl(bool_constant<is_nothrow_constructible_v<_Tp, _Arg> ||
!is_nothrow_move_constructible_v<_Tp>>{});
}
}
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);
},
*this, _VSTD::forward<_That>(__that));
}
}
};
template <class _Traits, _Trait = _Traits::__move_assignable_trait>
class _LIBCPP_TEMPLATE_VIS __move_assignment;
#define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, \
move_assignment) \
template <class... _Types> \
class _LIBCPP_TEMPLATE_VIS __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_TEMPLATE_VIS __copy_assignment;
#define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, \
copy_assignment) \
template <class... _Types> \
class _LIBCPP_TEMPLATE_VIS __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_TEMPLATE_VIS __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));
}
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
if constexpr (__all<is_nothrow_move_constructible_v<_Types>...>::value) {
this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
} else {
// 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 guarantee.
try {
this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
} catch (...) {
if (__tmp.__move_nothrow()) {
this->__generic_construct(*__rhs, _VSTD::move(__tmp));
}
throw;
}
}
#else
// this isn't consolidated with the `if constexpr` branch above due to
// `throw` being ill-formed with exceptions disabled even when discarded.
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()];
}
};
struct __no_narrowing_check {
template <class _Dest, class _Source>
using _Apply = __identity<_Dest>;
};
struct __narrowing_check {
template <class _Dest>
static auto __test_impl(_Dest (&&)[1]) -> __identity<_Dest>;
template <class _Dest, class _Source>
using _Apply _LIBCPP_NODEBUG_TYPE = decltype(__test_impl<_Dest>({std::declval<_Source>()}));
};
template <class _Dest, class _Source>
using __check_for_narrowing _LIBCPP_NODEBUG_TYPE =
typename _If<
#ifdef _LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT
false &&
#endif
is_arithmetic<_Dest>::value,
__narrowing_check,
__no_narrowing_check
>::template _Apply<_Dest, _Source>;
template <class _Tp, size_t _Idx>
struct __overload {
template <class _Up>
auto operator()(_Tp, _Up&&) const -> __check_for_narrowing<_Tp, _Up>;
};
template <class _Tp, size_t>
struct __overload_bool {
template <class _Up, class _Ap = __uncvref_t<_Up>>
auto operator()(bool, _Up&&) const
-> enable_if_t<is_same_v<_Ap, bool>, __identity<_Tp>>;
};
template <size_t _Idx>
struct __overload<bool, _Idx> : __overload_bool<bool, _Idx> {};
template <size_t _Idx>
struct __overload<bool const, _Idx> : __overload_bool<bool const, _Idx> {};
template <size_t _Idx>
struct __overload<bool volatile, _Idx> : __overload_bool<bool volatile, _Idx> {};
template <size_t _Idx>
struct __overload<bool const volatile, _Idx> : __overload_bool<bool const volatile, _Idx> {};
template <class ..._Bases>
struct __all_overloads : _Bases... {
void operator()() const;
using _Bases::operator()...;
};
template <class IdxSeq>
struct __make_overloads_imp;
template <size_t ..._Idx>
struct __make_overloads_imp<__tuple_indices<_Idx...> > {
template <class ..._Types>
using _Apply _LIBCPP_NODEBUG_TYPE = __all_overloads<__overload<_Types, _Idx>...>;
};
template <class ..._Types>
using _MakeOverloads _LIBCPP_NODEBUG_TYPE = typename __make_overloads_imp<
__make_indices_imp<sizeof...(_Types), 0> >::template _Apply<_Types...>;
template <class _Tp, class... _Types>
using __best_match_t =
typename invoke_result_t<_MakeOverloads<_Types...>, _Tp, _Tp>::type;
} // __variant_detail
template <class... _Types>
class _LIBCPP_TEMPLATE_VIS 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_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<__uncvref_t<_Arg>, variant>, int> = 0,
enable_if_t<!__is_inplace_type<__uncvref_t<_Arg>>::value, int> = 0,
enable_if_t<!__is_inplace_index<__uncvref_t<_Arg>>::value, 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,
class = enable_if_t<(_Ip < sizeof...(_Types)), int>,
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<__uncvref_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
_Tp& emplace(_Args&&... __args) {
return __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
_Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
return __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
_Tp& emplace(_Args&&... __args) {
return __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
_Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
return __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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
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 _Operator>
struct __convert_to_bool {
template <class _T1, class _T2>
_LIBCPP_INLINE_VISIBILITY constexpr bool operator()(_T1 && __t1, _T2&& __t2) const {
static_assert(std::is_convertible<decltype(_Operator{}(_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2))), bool>::value,
"the relational operator does not return a type which is implicitly convertible to bool");
return _Operator{}(_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2));
}
};
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(), __convert_to_bool<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(), __convert_to_bool<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(), __convert_to_bool<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(), __convert_to_bool<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(), __convert_to_bool<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(), __convert_to_bool<greater_equal<>>{}, __lhs, __rhs);
}
template <class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
constexpr decltype(auto) visit(_Vis&& __vis, _Vs&&... __vs) {
using __variant_detail::__visitation::__variant;
return __variant::__visit_value(_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Vs>(__vs)...);
}
struct _LIBCPP_TEMPLATE_VIS 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_TEMPLATE_VIS hash<
__enable_hash_helper<variant<_Types...>, remove_const_t<_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;
size_t __res =
__v.valueless_by_exception()
? 299792458 // Random value chosen by the universe upon creation
: __variant::__visit_alt(
[](const auto& __alt) {
using __alt_type = __uncvref_t<decltype(__alt)>;
using __value_type = remove_const_t<
typename __alt_type::__value_type>;
return hash<__value_type>{}(__alt.__value);
},
__v);
return __hash_combine(__res, hash<size_t>{}(__v.index()));
}
};
template <>
struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
using argument_type = monostate;
using result_type = size_t;
inline _LIBCPP_INLINE_VISIBILITY
result_type operator()(const argument_type&) const _NOEXCEPT {
return 66740831; // return a fundamentally attractive random value.
}
};
#endif // _LIBCPP_STD_VER > 14
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP_VARIANT
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