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Implement LWG-4012 common_view::begin/end are missing the simple-view check #4529

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Merged
merged 1 commit into from
Mar 28, 2024
Merged

Implement LWG-4012 common_view::begin/end are missing the simple-view check #4529

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8 changes: 6 additions & 2 deletions stl/inc/ranges
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Original file line number Diff line number Diff line change
Expand Up @@ -5285,7 +5285,9 @@ namespace ranges {
}

_NODISCARD constexpr auto begin() noexcept(
noexcept(_RANGES begin(_Base)) && is_nothrow_move_constructible_v<iterator_t<_Vw>>) /* strengthened */ {
noexcept(_RANGES begin(_Base)) && is_nothrow_move_constructible_v<iterator_t<_Vw>>) /* strengthened */
requires (!_Simple_view<_Vw>)
{
if constexpr (random_access_range<_Vw> && sized_range<_Vw>) {
return _RANGES begin(_Base);
} else {
Expand All @@ -5304,7 +5306,9 @@ namespace ranges {
}
}

_NODISCARD constexpr auto end() {
_NODISCARD constexpr auto end()
requires (!_Simple_view<_Vw>)
{
if constexpr (random_access_range<_Vw> && sized_range<_Vw>) {
return _RANGES begin(_Base) + _RANGES distance(_Base);
} else {
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31 changes: 31 additions & 0 deletions tests/std/tests/P0896R4_views_common/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -541,6 +541,34 @@ constexpr bool test_lwg3717() {
return true;
}

constexpr bool test_lwg_4012() {
struct simple_view_with_difference_on_const : ranges::view_interface<simple_view_with_difference_on_const> {
constexpr difference_type_only_iterator<int> begin() noexcept {
return {nullptr};
}
constexpr difference_type_only_sentinel<int> end() noexcept {
return {nullptr};
}
constexpr difference_type_only_iterator<int> begin() const noexcept {
return {p_};
}
constexpr difference_type_only_sentinel<int> end() const noexcept {
return {p_};
}

int* p_;
};

int n{};
auto cv = views::common(simple_view_with_difference_on_const{{}, &n});

assert(cv.begin() == as_const(cv).begin());
assert(cv.begin() == as_const(cv).end());
assert(as_const(cv).begin() == cv.end());

return true;
}

int main() {
// Get full instantiation coverage
static_assert((test_in<instantiator, const int>(), true));
Expand All @@ -551,4 +579,7 @@ int main() {

assert(test_lwg3717<int>());
assert(test_lwg3717<const int>());

static_assert(test_lwg_4012());
test_lwg_4012();
}