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Don't move from contained value of optional<const T> #2460

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merged 3 commits into from
Mar 4, 2022
Merged

Don't move from contained value of optional<const T> #2460

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be9f1fa
Don't move from contained value of optional<const T>
CaseyCarter Jan 6, 2022
7c9c10a
Merge branch 'main' into optional_const
StephanTLavavej Feb 19, 2022
39bebbd
Capitalize template parameter.
StephanTLavavej Feb 19, 2022
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63 changes: 34 additions & 29 deletions stl/inc/optional
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Original file line number Diff line number Diff line change
Expand Up @@ -156,24 +156,52 @@ struct _Optional_construct_base : _Optional_destruct_base<_Ty> {

template <class _Self>
_CONSTEXPR20 void _Construct_from(_Self&& _Right) noexcept(
is_nothrow_constructible_v<_Ty, decltype((_STD forward<_Self>(_Right)._Value))>) {
is_nothrow_constructible_v<_Ty, decltype(*_STD forward<_Self>(_Right))>) {
// initialize contained value from _Right iff it contains a value
if (_Right._Has_value) {
_Construct(_STD forward<_Self>(_Right)._Value);
_Construct(*_STD forward<_Self>(_Right));
}
}

template <class _Self>
_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))>) {
is_nothrow_constructible_v<_Ty, decltype(*_STD forward<_Self>(_Right))>&&
is_nothrow_assignable_v<_Ty&, decltype(*_STD forward<_Self>(_Right))>) {
// assign/initialize/destroy contained value from _Right
if (_Right._Has_value) {
_Assign(_STD forward<_Self>(_Right)._Value);
_Assign(*_STD forward<_Self>(_Right));
} else {
this->reset();
}
}

_NODISCARD constexpr _Ty& operator*() & noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return this->_Value;
}

_NODISCARD constexpr const _Ty& operator*() const& noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return this->_Value;
}

_NODISCARD constexpr _Ty&& operator*() && noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return _STD move(this->_Value);
}

_NODISCARD constexpr const _Ty&& operator*() const&& noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return _STD move(this->_Value);
}
};

template <class _Ty>
Expand Down Expand Up @@ -379,30 +407,7 @@ public:
return _STD addressof(this->_Value);
}

_NODISCARD constexpr const _Ty& operator*() const& noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return this->_Value;
}
_NODISCARD constexpr _Ty& operator*() & noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return this->_Value;
}
_NODISCARD constexpr _Ty&& operator*() && noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return _STD move(this->_Value);
}
_NODISCARD constexpr const _Ty&& operator*() const&& noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(this->_Has_value, "Cannot access value of empty optional");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return _STD move(this->_Value);
}
using _Mybase::operator*;

constexpr explicit operator bool() const noexcept {
return this->_Has_value;
Expand Down
43 changes: 43 additions & 0 deletions tests/std/tests/P0220R1_optional/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7382,6 +7382,47 @@ namespace msvc {
(void) t;
}
} // namespace vso614907

namespace gh2458 {
// optional<const meow> o = std::move(lvalue_optional_const_meow);
// was moving from the contained const object
enum class action { none, copy, move };
action last = action::none;

struct Copyable {
Copyable() = default;
Copyable(const Copyable&) {
last = action::copy;
}
Copyable(Copyable&&) {
last = action::move;
}
};

struct ConstMovable {
ConstMovable() = default;
ConstMovable(const ConstMovable&) {
last = action::copy;
}
ConstMovable(const ConstMovable&&) {
last = action::move;
}
};

template <class T, action result>
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void testMove() {
std::optional<T> orig{std::in_place};
std::optional<T> moved = std::move(orig);
assert(last == result);
}

void run_test() {
testMove<Copyable, action::move>();
testMove<const Copyable, action::copy>();
testMove<ConstMovable, action::move>();
testMove<const ConstMovable, action::move>();
}
} // namespace gh2458
} // namespace msvc

int main() {
Expand Down Expand Up @@ -7478,4 +7519,6 @@ int main() {
msvc::vso406124::run_test();
msvc::vso508126::run_test();
msvc::vso614907::run_test();

msvc::gh2458::run_test();
}