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LWG-3847 ranges::to can still return views #3479

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merged 5 commits into from
Feb 23, 2023
Merged

LWG-3847 ranges::to can still return views #3479

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7c4e44c
Prevent to from returning view
mlemacio Feb 18, 2023
ee10651
Moved cv check into static assert
mlemacio Feb 18, 2023
4a00085
Better static assert messages
mlemacio Feb 21, 2023
cb1eb6b
Added class type restriction
mlemacio Feb 21, 2023
7ce1ed7
Code review feedback: Fix citations slightly.
StephanTLavavej Feb 22, 2023
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9 changes: 9 additions & 0 deletions stl/inc/ranges
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Original file line number Diff line number Diff line change
Expand Up @@ -8402,6 +8402,9 @@ namespace ranges {
_EXPORT_STD template <class _Container, input_range _Rng, class... _Types>
requires (!view<_Container>)
_NODISCARD constexpr _Container to(_Rng&& _Range, _Types&&... _Args) {
static_assert(!is_const_v<_Container>, "C must not be const. ([range.utility.conv.to])");
static_assert(!is_volatile_v<_Container>, "C must not be volatile. ([range.utility.conv.to])");
static_assert(is_class_v<_Container>, "C must be a class type. ([range.utility.conv.to])");
if constexpr (_Converts_direct_constructible<_Rng, _Container, _Types...>) {
return _Container(_STD forward<_Rng>(_Range), _STD forward<_Types>(_Args)...);
} else if constexpr (_Converts_tag_constructible<_Rng, _Container, _Types...>) {
Expand All @@ -8427,6 +8430,9 @@ namespace ranges {

template <class _Container>
struct _To_class_fn {
_STL_INTERNAL_STATIC_ASSERT(!is_const_v<_Container>);
_STL_INTERNAL_STATIC_ASSERT(!is_volatile_v<_Container>);
_STL_INTERNAL_STATIC_ASSERT(is_class_v<_Container>);
_STL_INTERNAL_STATIC_ASSERT(!view<_Container>);

template <input_range _Rng, class... _Types>
Expand All @@ -8440,6 +8446,9 @@ namespace ranges {
_EXPORT_STD template <class _Container, class... _Types>
requires (!view<_Container>)
_NODISCARD constexpr auto to(_Types&&... _Args) {
static_assert(!is_const_v<_Container>, "C must not be const. ([range.utility.conv.adaptors])");
static_assert(!is_volatile_v<_Container>, "C must not be volatile. ([range.utility.conv.adaptors])");
static_assert(is_class_v<_Container>, "C must be a class type. ([range.utility.conv.adaptors])");
return _Range_closure<_To_class_fn<_Container>, decay_t<_Types>...>{_STD forward<_Types>(_Args)...};
}

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