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P2231R1 Completing constexpr In optional And variant (#2005)
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Co-authored-by: Casey Carter <[email protected]>
Co-authored-by: Stephan T. Lavavej <[email protected]>
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@miscco @CaseyCarter @StephanTLavavej
3 people authored Aug 26, 2021
1 parent 4d5d925 commit 96a4c16
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Showing 12 changed files with 479 additions and 79 deletions.
36 changes: 19 additions & 17 deletions stl/inc/optional
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ struct _Optional_destruct_base { // either contains a value of _Ty or is empty (
constexpr explicit _Optional_destruct_base(in_place_t, _Types&&... _Args)
: _Value(_STD forward<_Types>(_Args)...), _Has_value{true} {} // initialize contained value with _Args...

void reset() noexcept {
_CONSTEXPR20 void reset() noexcept {
_Has_value = false;
}
};
Expand All @@ -88,7 +88,7 @@ struct _Optional_destruct_base<_Ty, false> { // either contains a value of _Ty o
};
bool _Has_value;

~_Optional_destruct_base() noexcept {
_CONSTEXPR20 ~_Optional_destruct_base() noexcept {
if (_Has_value) {
_Destroy_in_place(_Value);
}
Expand All @@ -105,7 +105,7 @@ struct _Optional_destruct_base<_Ty, false> { // either contains a value of _Ty o
_Optional_destruct_base& operator=(const _Optional_destruct_base&) = default;
_Optional_destruct_base& operator=(_Optional_destruct_base&&) = default;

void reset() noexcept {
_CONSTEXPR20 void reset() noexcept {
if (_Has_value) {
_Destroy_in_place(_Value);
_Has_value = false;
Expand All @@ -119,15 +119,16 @@ struct _Optional_construct_base : _Optional_destruct_base<_Ty> {
using _Optional_destruct_base<_Ty>::_Optional_destruct_base;

template <class... _Types>
_Ty& _Construct(_Types&&... _Args) { // transition from the empty to the value-containing state
_CONSTEXPR20 _Ty& _Construct(_Types&&... _Args) {
// transition from the empty to the value-containing state
_STL_INTERNAL_CHECK(!this->_Has_value);
_Construct_in_place(this->_Value, _STD forward<_Types>(_Args)...);
this->_Has_value = true;
return this->_Value;
}

template <class _Ty2>
void _Assign(_Ty2&& _Right) { // assign / initialize the contained value from _Right
_CONSTEXPR20 void _Assign(_Ty2&& _Right) { // assign / initialize the contained value from _Right
if (this->_Has_value) {
this->_Value = _STD forward<_Ty2>(_Right);
} else {
Expand All @@ -136,7 +137,7 @@ struct _Optional_construct_base : _Optional_destruct_base<_Ty> {
}

template <class _Self>
void _Construct_from(_Self&& _Right) noexcept(
_CONSTEXPR20 void _Construct_from(_Self&& _Right) noexcept(
is_nothrow_constructible_v<_Ty, decltype((_STD forward<_Self>(_Right)._Value))>) {
// initialize contained value from _Right iff it contains a value
if (_Right._Has_value) {
Expand All @@ -145,7 +146,7 @@ struct _Optional_construct_base : _Optional_destruct_base<_Ty> {
}

template <class _Self>
void _Assign_from(_Self&& _Right) noexcept(
_CONSTEXPR20 void _Assign_from(_Self&& _Right) noexcept(
is_nothrow_constructible_v<_Ty, decltype((_STD forward<_Self>(_Right)._Value))>&&
is_nothrow_assignable_v<_Ty&, decltype((_STD forward<_Self>(_Right)._Value))>) {
// assign/initialize/destroy contained value from _Right
Expand Down Expand Up @@ -208,7 +209,7 @@ public:
#if _HAS_CONDITIONAL_EXPLICIT
template <class _Ty2,
enable_if_t<conjunction_v<_AllowUnwrapping<_Ty2>, is_constructible<_Ty, const _Ty2&>>, int> = 0>
explicit(!is_convertible_v<const _Ty2&, _Ty>) optional(const optional<_Ty2>& _Right) {
_CONSTEXPR20 explicit(!is_convertible_v<const _Ty2&, _Ty>) optional(const optional<_Ty2>& _Right) {
if (_Right) {
this->_Construct(*_Right);
}
Expand All @@ -234,7 +235,7 @@ public:

#if _HAS_CONDITIONAL_EXPLICIT
template <class _Ty2, enable_if_t<conjunction_v<_AllowUnwrapping<_Ty2>, is_constructible<_Ty, _Ty2>>, int> = 0>
explicit(!is_convertible_v<_Ty2, _Ty>) optional(optional<_Ty2>&& _Right) {
_CONSTEXPR20 explicit(!is_convertible_v<_Ty2, _Ty>) optional(optional<_Ty2>&& _Right) {
if (_Right) {
this->_Construct(_STD move(*_Right));
}
Expand All @@ -258,7 +259,7 @@ public:
}
#endif // ^^^ !_HAS_CONDITIONAL_EXPLICIT ^^^

optional& operator=(nullopt_t) noexcept {
_CONSTEXPR20 optional& operator=(nullopt_t) noexcept {
reset();
return *this;
}
Expand All @@ -267,7 +268,7 @@ public:
negation<conjunction<is_scalar<_Ty>, is_same<_Ty, decay_t<_Ty2>>>>,
is_constructible<_Ty, _Ty2>, is_assignable<_Ty&, _Ty2>>,
int> = 0>
optional& operator=(_Ty2&& _Right) {
_CONSTEXPR20 optional& operator=(_Ty2&& _Right) {
this->_Assign(_STD forward<_Ty2>(_Right));
return *this;
}
Expand All @@ -281,7 +282,7 @@ public:
template <class _Ty2, enable_if_t<conjunction_v<_AllowUnwrappingAssignment<_Ty2>,
is_constructible<_Ty, const _Ty2&>, is_assignable<_Ty&, const _Ty2&>>,
int> = 0>
optional& operator=(const optional<_Ty2>& _Right) {
_CONSTEXPR20 optional& operator=(const optional<_Ty2>& _Right) {
if (_Right) {
this->_Assign(*_Right);
} else {
Expand All @@ -294,7 +295,7 @@ public:
template <class _Ty2, enable_if_t<conjunction_v<_AllowUnwrappingAssignment<_Ty2>, is_constructible<_Ty, _Ty2>,
is_assignable<_Ty&, _Ty2>>,
int> = 0>
optional& operator=(optional<_Ty2>&& _Right) {
_CONSTEXPR20 optional& operator=(optional<_Ty2>&& _Right) {
if (_Right) {
this->_Assign(_STD move(*_Right));
} else {
Expand All @@ -305,19 +306,20 @@ public:
}

template <class... _Types>
_Ty& emplace(_Types&&... _Args) {
_CONSTEXPR20 _Ty& emplace(_Types&&... _Args) {
reset();
return this->_Construct(_STD forward<_Types>(_Args)...);
}

template <class _Elem, class... _Types,
enable_if_t<is_constructible_v<_Ty, initializer_list<_Elem>&, _Types...>, int> = 0>
_Ty& emplace(initializer_list<_Elem> _Ilist, _Types&&... _Args) {
_CONSTEXPR20 _Ty& emplace(initializer_list<_Elem> _Ilist, _Types&&... _Args) {
reset();
return this->_Construct(_Ilist, _STD forward<_Types>(_Args)...);
}

void swap(optional& _Right) noexcept(is_nothrow_move_constructible_v<_Ty>&& is_nothrow_swappable_v<_Ty>) {
_CONSTEXPR20 void swap(optional& _Right) noexcept(
is_nothrow_move_constructible_v<_Ty>&& is_nothrow_swappable_v<_Ty>) {
static_assert(is_move_constructible_v<_Ty>,
"optional<T>::swap requires T to be move constructible (N4828 [optional.swap]/1).");
static_assert(!is_move_constructible_v<_Ty> || is_swappable_v<_Ty>,
Expand Down Expand Up @@ -654,7 +656,7 @@ _NODISCARD constexpr compare_three_way_result_t<_Ty1, _Ty2>
#endif // __cpp_lib_concepts

template <class _Ty, enable_if_t<is_move_constructible_v<_Ty> && is_swappable_v<_Ty>, int> = 0>
void swap(optional<_Ty>& _Left, optional<_Ty>& _Right) noexcept(noexcept(_Left.swap(_Right))) {
_CONSTEXPR20 void swap(optional<_Ty>& _Left, optional<_Ty>& _Right) noexcept(noexcept(_Left.swap(_Right))) {
_Left.swap(_Right);
}

Expand Down
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