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Implement LWG-3470: convertible-to-non-slicing seems to reject valid case #2414

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 3 commits into from
Dec 17, 2021
Merged

Implement LWG-3470: convertible-to-non-slicing seems to reject valid case #2414

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4b48ee1
modify convertible-to-non-slicing
fsb4000 Dec 13, 2021
76d0087
infer size of arrays
fsb4000 Dec 13, 2021
9ebf855
Style nitpicks.
StephanTLavavej Dec 14, 2021
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9 changes: 6 additions & 3 deletions stl/inc/xutility
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Original file line number Diff line number Diff line change
Expand Up @@ -3246,11 +3246,14 @@ _NODISCARD constexpr const tuple_element_t<_Index, tuple<_Types...>>&& get(const

namespace ranges {
// clang-format off
template <class _From, class _To>
concept _Uses_nonqualification_pointer_conversion =
is_pointer_v<_From> && is_pointer_v<_To>
&& !convertible_to<remove_pointer_t<_From>(*)[], remove_pointer_t<_To>(*)[]>;

template <class _From, class _To>
concept _Convertible_to_non_slicing = convertible_to<_From, _To>
&& !(is_pointer_v<decay_t<_From>>
&& is_pointer_v<decay_t<_To>>
&& _Not_same_as<remove_pointer_t<decay_t<_From>>, remove_pointer_t<decay_t<_To>>>);
&& !_Uses_nonqualification_pointer_conversion<decay_t<_From>, decay_t<_To>>;

template <class _Ty>
concept _Pair_like = !is_reference_v<_Ty> && requires(_Ty __t) {
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6 changes: 6 additions & 0 deletions tests/std/tests/P0896R4_ranges_subrange/test.compile.pass.cpp
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Expand Up @@ -23,6 +23,12 @@ using std::output_iterator_tag, std::input_iterator_tag, std::forward_iterator_t

int main() {} // COMPILE-ONLY

void test_LWG_3470() {
int a[] = {1, 2, 3};
int* b[] = {&a[2], &a[0], &a[1]};
[[maybe_unused]] auto c = std::ranges::subrange<const int* const*>(b);
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}

struct empty {};

namespace test_view_interface {
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