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Implement LWG-3712: chunk_view and slide_view should not be default_initializable #2943

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merged 6 commits into from
Jul 28, 2022
Merged

Implement LWG-3712: chunk_view and slide_view should not be default_initializable #2943

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cdc0383
Test non-default-initializability of slide_view (LWG-3712)
frederick-vs-ja Jul 21, 2022
be9d561
Test non-default-initializability of chunk_view (LWG-3712)
frederick-vs-ja Jul 21, 2022
01dc837
Implement LWG-3712
frederick-vs-ja Jul 21, 2022
3a088a1
Drop mention to the LWG issue number
frederick-vs-ja Jul 25, 2022
f100526
Drop mention to the LWG issue number
frederick-vs-ja Jul 25, 2022
f9ad48d
Don't redundantly check !default_initializable
CaseyCarter Jul 27, 2022
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24 changes: 6 additions & 18 deletions stl/inc/ranges
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Original file line number Diff line number Diff line change
Expand Up @@ -5248,8 +5248,8 @@ namespace ranges {
requires input_range<_Vw>
class chunk_view : public view_interface<chunk_view<_Vw>> {
private:
/* [[no_unique_address]] */ _Vw _Range{};
range_difference_t<_Vw> _Count = 0;
/* [[no_unique_address]] */ _Vw _Range;
range_difference_t<_Vw> _Count;
range_difference_t<_Vw> _Remainder = 0;
_Non_propagating_cache<iterator_t<_Vw>> _Current{};

Expand Down Expand Up @@ -5430,10 +5430,6 @@ namespace ranges {
};

public:
// clang-format off
chunk_view() requires default_initializable<_Vw> = default;
// clang-format on

constexpr explicit chunk_view(_Vw _Range_, const range_difference_t<_Vw> _Count_) noexcept(
is_nothrow_move_constructible_v<_Vw>) /* strengthened */
: _Range(_STD move(_Range_)), _Count{_Count_} {
Expand Down Expand Up @@ -5477,8 +5473,8 @@ namespace ranges {
requires forward_range<_Vw>
class chunk_view<_Vw> : public view_interface<chunk_view<_Vw>> {
private:
/* [[no_unique_address]] */ _Vw _Range{};
range_difference_t<_Vw> _Count = 0;
/* [[no_unique_address]] */ _Vw _Range;
range_difference_t<_Vw> _Count;

template <bool _Const>
class _Iterator {
Expand Down Expand Up @@ -5690,10 +5686,6 @@ namespace ranges {
};

public:
// clang-format off
chunk_view() requires default_initializable<_Vw> = default;
// clang-format on

constexpr explicit chunk_view(_Vw _Range_, const range_difference_t<_Vw> _Count_) noexcept(
is_nothrow_move_constructible_v<_Vw>) /* strengthened */
: _Range(_STD move(_Range_)), _Count{_Count_} {
Expand Down Expand Up @@ -5818,8 +5810,8 @@ namespace ranges {
requires view<_Vw>
class slide_view : public _Cached_position_t<!_Slide_caches_nothing<_Vw>, _Vw, slide_view<_Vw>> {
private:
/* [[no_unique_address]] */ _Vw _Range{};
range_difference_t<_Vw> _Count = 0;
/* [[no_unique_address]] */ _Vw _Range;
range_difference_t<_Vw> _Count;

template <class>
class _Iter_base {};
Expand Down Expand Up @@ -6052,10 +6044,6 @@ namespace ranges {
};

public:
// clang-format off
slide_view() requires default_initializable<_Vw> = default;
// clang-format on

constexpr explicit slide_view(_Vw _Range_, const range_difference_t<_Vw> _Count_) noexcept(
is_nothrow_move_constructible_v<_Vw>) /* strengthened */
: _Range(_STD move(_Range_)), _Count{_Count_} {}
Expand Down
9 changes: 9 additions & 0 deletions tests/std/tests/P2442R1_views_chunk/test.cpp
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Expand Up @@ -35,6 +35,9 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
STATIC_ASSERT(forward_range<R> == forward_range<Rng>);
STATIC_ASSERT(bidirectional_range<R> == bidirectional_range<Rng>);
STATIC_ASSERT(random_access_range<R> == random_access_range<Rng>);
// Validate non-default-initializability
STATIC_ASSERT(!is_default_constructible_v<R>);
STATIC_ASSERT(!default_initializable<R>);
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No change requested: test_one() is called for both input-only and forward ranges, so this covers the LWG issue's modifications to both the primary template and the specialization for forward ranges.

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// Validate borrowed_range
STATIC_ASSERT(ranges::borrowed_range<R> == (ranges::borrowed_range<V> && forward_range<V>) );

Expand All @@ -59,6 +62,9 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
using RC = chunk_view<views::all_t<const remove_reference_t<Rng>&>>;
constexpr bool is_noexcept = !is_view || is_nothrow_copy_constructible_v<V>;

STATIC_ASSERT(!is_default_constructible_v<RC>);
STATIC_ASSERT(!default_initializable<RC>);

STATIC_ASSERT(same_as<decltype(views::chunk(as_const(rng), 2)), RC>);
STATIC_ASSERT(noexcept(views::chunk(as_const(rng), 2)) == is_noexcept);

Expand All @@ -72,6 +78,9 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
using RS = chunk_view<views::all_t<remove_reference_t<Rng>>>;
constexpr bool is_noexcept = is_nothrow_move_constructible_v<V>;

STATIC_ASSERT(!is_default_constructible_v<RS>);
STATIC_ASSERT(!default_initializable<RS>);

STATIC_ASSERT(same_as<decltype(views::chunk(move(rng), 2)), RS>);
STATIC_ASSERT(noexcept(views::chunk(move(rng), 2)) == is_noexcept);

Expand Down
10 changes: 10 additions & 0 deletions tests/std/tests/P2442R1_views_slide/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,10 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
STATIC_ASSERT(bidirectional_range<R> == bidirectional_range<Rng>);
STATIC_ASSERT(random_access_range<R> == random_access_range<Rng>);

// Validate non-default-initializability
STATIC_ASSERT(!is_default_constructible_v<R>);
STATIC_ASSERT(!default_initializable<R>);

// Validate borrowed_range
static_assert(ranges::borrowed_range<R> == ranges::borrowed_range<V>);

Expand All @@ -63,6 +67,9 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
using RC = slide_view<views::all_t<const remove_reference_t<Rng>&>>;
constexpr bool is_noexcept = !is_view || is_nothrow_copy_constructible_v<V>;

STATIC_ASSERT(!is_default_constructible_v<RC>);
STATIC_ASSERT(!default_initializable<RC>);

STATIC_ASSERT(same_as<decltype(views::slide(as_const(rng), 4)), RC>);
STATIC_ASSERT(noexcept(views::slide(as_const(rng), 4)) == is_noexcept);

Expand All @@ -76,6 +83,9 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
using RS = slide_view<views::all_t<remove_reference_t<Rng>>>;
constexpr bool is_noexcept = is_nothrow_move_constructible_v<V>;

STATIC_ASSERT(!is_default_constructible_v<RS>);
STATIC_ASSERT(!default_initializable<RS>);

STATIC_ASSERT(same_as<decltype(views::slide(move(rng), 4)), RS>);
STATIC_ASSERT(noexcept(views::slide(move(rng), 4)) == is_noexcept);

Expand Down