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[libc++] Refactor optional constructors to use conditional explicit #152999

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[libc++] Refactor optional constructors to use conditional explicit #152999

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20 changes: 0 additions & 20 deletions libcxx/include/__tuple/sfinae_helpers.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,26 +17,6 @@

_LIBCPP_BEGIN_NAMESPACE_STD

#ifndef _LIBCPP_CXX03_LANG

struct _LIBCPP_EXPORTED_FROM_ABI __check_tuple_constructor_fail {
static _LIBCPP_HIDE_FROM_ABI constexpr bool __enable_explicit_default() { return false; }
static _LIBCPP_HIDE_FROM_ABI constexpr bool __enable_implicit_default() { return false; }
template <class...>
static _LIBCPP_HIDE_FROM_ABI constexpr bool __enable_explicit() {
return false;
}
template <class...>
static _LIBCPP_HIDE_FROM_ABI constexpr bool __enable_implicit() {
return false;
}
template <class...>
static _LIBCPP_HIDE_FROM_ABI constexpr bool __enable_assign() {
return false;
}
};
#endif // !defined(_LIBCPP_CXX03_LANG)

#if _LIBCPP_STD_VER >= 17

template <bool _CanCopy, bool _CanMove>
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125 changes: 44 additions & 81 deletions libcxx/include/optional
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Original file line number Diff line number Diff line change
Expand Up @@ -604,69 +604,20 @@ private:
static_assert(!is_array_v<value_type>, "instantiation of optional with an array type is ill-formed");

// LWG2756: conditionally explicit conversion from _Up
struct _CheckOptionalArgsConstructor {
template <class _Up>
_LIBCPP_HIDE_FROM_ABI static constexpr bool __enable_implicit() {
return is_constructible_v<_Tp, _Up&&> && is_convertible_v<_Up&&, _Tp>;
}

template <class _Up>
_LIBCPP_HIDE_FROM_ABI static constexpr bool __enable_explicit() {
return is_constructible_v<_Tp, _Up&&> && !is_convertible_v<_Up&&, _Tp>;
}
};
template <class _Up>
using _CheckOptionalArgsCtor _LIBCPP_NODEBUG =
_If< _IsNotSame<__remove_cvref_t<_Up>, in_place_t>::value && _IsNotSame<__remove_cvref_t<_Up>, optional>::value &&
(!is_same_v<remove_cv_t<_Tp>, bool> || !__is_std_optional<__remove_cvref_t<_Up>>::value),
_CheckOptionalArgsConstructor,
__check_tuple_constructor_fail >;
template <class _QualUp>
struct _CheckOptionalLikeConstructor {
template <class _Up, class _Opt = optional<_Up>>
using __check_constructible_from_opt _LIBCPP_NODEBUG =
_Or< is_constructible<_Tp, _Opt&>,
is_constructible<_Tp, _Opt const&>,
is_constructible<_Tp, _Opt&&>,
is_constructible<_Tp, _Opt const&&>,
is_convertible<_Opt&, _Tp>,
is_convertible<_Opt const&, _Tp>,
is_convertible<_Opt&&, _Tp>,
is_convertible<_Opt const&&, _Tp> >;
template <class _Up, class _Opt = optional<_Up>>
using __check_assignable_from_opt _LIBCPP_NODEBUG =
_Or< is_assignable<_Tp&, _Opt&>,
is_assignable<_Tp&, _Opt const&>,
is_assignable<_Tp&, _Opt&&>,
is_assignable<_Tp&, _Opt const&&> >;
template <class _Up, class _QUp = _QualUp>
_LIBCPP_HIDE_FROM_ABI static constexpr bool __enable_implicit() {
return is_convertible<_QUp, _Tp>::value &&
(is_same_v<remove_cv_t<_Tp>, bool> || !__check_constructible_from_opt<_Up>::value);
}
template <class _Up, class _QUp = _QualUp>
_LIBCPP_HIDE_FROM_ABI static constexpr bool __enable_explicit() {
return !is_convertible<_QUp, _Tp>::value &&
(is_same_v<remove_cv_t<_Tp>, bool> || !__check_constructible_from_opt<_Up>::value);
}
template <class _Up, class _QUp = _QualUp>
_LIBCPP_HIDE_FROM_ABI static constexpr bool __enable_assign() {
// Construction and assignability of _QUp to _Tp has already been
// checked.
return !__check_constructible_from_opt<_Up>::value && !__check_assignable_from_opt<_Up>::value;
}
};
template <class _Up, class _Opt = optional<_Up>>
using __check_constructible_from_opt _LIBCPP_NODEBUG =
_Or<is_constructible<_Tp, _Opt&>,
is_constructible<_Tp, _Opt const&>,
is_constructible<_Tp, _Opt&&>,
is_constructible<_Tp, _Opt const&&>>;

template <class _Up, class _QualUp>
using _CheckOptionalLikeCtor _LIBCPP_NODEBUG =
_If< _And< _IsNotSame<_Up, _Tp>, is_constructible<_Tp, _QualUp> >::value,
_CheckOptionalLikeConstructor<_QualUp>,
__check_tuple_constructor_fail >;
template <class _Up, class _QualUp>
using _CheckOptionalLikeAssign _LIBCPP_NODEBUG =
_If< _And< _IsNotSame<_Up, _Tp>, is_constructible<_Tp, _QualUp>, is_assignable<_Tp&, _QualUp> >::value,
_CheckOptionalLikeConstructor<_QualUp>,
__check_tuple_constructor_fail >;
template <class _Up, class _Opt = optional<_Up>>
using __check_assignable_from_opt _LIBCPP_NODEBUG =
_Or<is_assignable<_Tp&, _Opt&>,
is_assignable<_Tp&, _Opt const&>,
is_assignable<_Tp&, _Opt&&>,
is_assignable<_Tp&, _Opt const&&>>;

public:
_LIBCPP_HIDE_FROM_ABI constexpr optional() noexcept {}
Expand All @@ -686,30 +637,34 @@ public:
_LIBCPP_HIDE_FROM_ABI constexpr explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
: __base(in_place, __il, std::forward<_Args>(__args)...) {}

template <class _Up = value_type,
enable_if_t<_CheckOptionalArgsCtor<_Up>::template __enable_implicit<_Up>(), int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr optional(_Up&& __v) : __base(in_place, std::forward<_Up>(__v)) {}

template <class _Up, enable_if_t<_CheckOptionalArgsCtor<_Up>::template __enable_explicit<_Up>(), int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr explicit optional(_Up&& __v) : __base(in_place, std::forward<_Up>(__v)) {}
template <class _Up,
class _DependentU = enable_if_t<
!is_same_v<__remove_cvref_t<_Up>, in_place_t> && !is_same_v<__remove_cvref_t<_Up>, optional> &&
(!is_same_v<remove_cv_t<_Tp>, bool> || !__is_std_optional<__remove_cvref_t<_Up>>::value),
_Up>,
enable_if_t<is_constructible_v<_Tp, _DependentU>, int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_Up&&, _Tp>) optional(_Up&& __v)
: __base(in_place, std::forward<_Up>(__v)) {}

// LWG2756: conditionally explicit conversion from const optional<_Up>&
template <class _Up, enable_if_t<_CheckOptionalLikeCtor<_Up, _Up const&>::template __enable_implicit<_Up>(), int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 optional(const optional<_Up>& __v) {
this->__construct_from(__v);
}
template <class _Up, enable_if_t<_CheckOptionalLikeCtor<_Up, _Up const&>::template __enable_explicit<_Up>(), int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit optional(const optional<_Up>& __v) {
template <class _Up,
class _DependentU = enable_if_t<!is_same_v<_Up, _Tp>, _Up>,
enable_if_t<is_constructible_v<_Tp, const _DependentU&> &&
(is_same_v<remove_cv_t<_Tp>, bool> || !__check_constructible_from_opt<_DependentU>::value),
int> = 0>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX20 explicit(!is_convertible_v<const _Up&, _Tp>) optional(const optional<_Up>& __v) {
this->__construct_from(__v);
}

// LWG2756: conditionally explicit conversion from optional<_Up>&&
template <class _Up, enable_if_t<_CheckOptionalLikeCtor<_Up, _Up&&>::template __enable_implicit<_Up>(), int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 optional(optional<_Up>&& __v) {
this->__construct_from(std::move(__v));
}
template <class _Up, enable_if_t<_CheckOptionalLikeCtor<_Up, _Up&&>::template __enable_explicit<_Up>(), int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit optional(optional<_Up>&& __v) {
template <class _Up,
class _DependentU = enable_if_t<!is_same_v<_Up, _Tp>, _Up>,
enable_if_t<is_constructible_v<_Tp, _DependentU&&> &&
(is_same_v<remove_cv_t<_Tp>, bool> || !__check_constructible_from_opt<_DependentU>::value),
int> = 0>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX20 explicit(!is_convertible_v<_Up&&, _Tp>) optional(optional<_Up>&& __v) {
this->__construct_from(std::move(__v));
}

Expand Down Expand Up @@ -746,14 +701,22 @@ public:
}

// LWG2756
template <class _Up, enable_if_t<_CheckOptionalLikeAssign<_Up, _Up const&>::template __enable_assign<_Up>(), int> = 0>
template <class _Up,
class _DependentU = enable_if_t<!is_same_v<_Tp, _Up>, _Up>,
enable_if_t<is_constructible_v<_Tp, const _DependentU&> && is_assignable_v<_Tp&, const _DependentU&> &&
!__check_constructible_from_opt<_Up>::value && !__check_assignable_from_opt<_Up>::value,
int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 optional& operator=(const optional<_Up>& __v) {
this->__assign_from(__v);
return *this;
}

// LWG2756
template <class _Up, enable_if_t<_CheckOptionalLikeCtor<_Up, _Up&&>::template __enable_assign<_Up>(), int> = 0>
template <class _Up,
class _DependentU = enable_if_t<!is_same_v<_Tp, _Up>, _Up>,
enable_if_t<is_constructible_v<_Tp, _DependentU&&> && is_assignable_v<_Tp&, _DependentU&&> &&
!__check_constructible_from_opt<_Up>::value && !__check_assignable_from_opt<_Up>::value,
int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 optional& operator=(optional<_Up>&& __v) {
this->__assign_from(std::move(__v));
return *this;
Expand Down
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