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LWG-3850: views::as_const on empty_view<T> should return empty_view<const T> #3423

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Merged
merged 4 commits into from
Feb 14, 2023
Merged

LWG-3850: views::as_const on empty_view<T> should return empty_view<const T> #3423

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de0c756
Implement LWG-3850
JMazurkiewicz Feb 12, 2023
b7e3e7d
Remove extraneous `std::`-qualifications
CaseyCarter Feb 12, 2023
db10621
Supress "dereferencing NULL pointer" static analysis wanrings
CaseyCarter Feb 12, 2023
db6b039
Properly handle empty_view<cv-T>
CaseyCarter Feb 12, 2023
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6 changes: 5 additions & 1 deletion stl/inc/ranges
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Original file line number Diff line number Diff line change
Expand Up @@ -5408,7 +5408,7 @@ namespace ranges {

class _As_const_fn : public _Pipe::_Base<_As_const_fn> {
private:
enum class _St { _None, _All, _Reconstruct_span, _Reconstruct_ref, _Ref, _As_const };
enum class _St { _None, _All, _Empty, _Reconstruct_span, _Reconstruct_ref, _Ref, _As_const };

template <class>
static constexpr bool _Can_reconstruct_ref_view_v = false;
Expand All @@ -5423,6 +5423,8 @@ namespace ranges {

if constexpr (constant_range<views::all_t<_Rng>>) {
return {_St::_All, noexcept(views::all(_STD declval<_Rng>()))};
} else if constexpr (_Is_specialization_v<_Ty, empty_view>) {
return {_St::_Empty, true};
} else if constexpr (_Is_span_v<_Ty>) {
return {_St::_Reconstruct_span, true};
} else if constexpr (_Can_reconstruct_ref_view_v<_Ty>) {
Expand All @@ -5448,6 +5450,8 @@ namespace ranges {

if constexpr (_Strat == _St::_All) {
return views::all(_STD forward<_Rng>(_Range));
} else if constexpr (_Strat == _St::_Empty) {
return empty_view<const remove_reference_t<range_reference_t<_Rng>>>{};
} else if constexpr (_Strat == _St::_Reconstruct_span) {
return span<const typename _Ty::element_type, _Ty::extent>{_STD forward<_Rng>(_Range)};
} else if constexpr (_Strat == _St::_Reconstruct_ref) {
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