Implement LWG-3712: chunk_view and slide_view should not be `defa…

…ult_initializable` (#2943) Co-authored-by: Casey Carter <[email protected]>
microsoft · Jul 28, 2022 · 374fc90 · 374fc90
1 parent f8a9c6f
commit 374fc90
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Showing 3 changed files with 21 additions and 18 deletions.
diff --git a/stl/inc/ranges b/stl/inc/ranges
@@ -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{};
 
@@ -5431,10 +5431,6 @@ 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_} {
@@ -5478,8 +5474,8 @@ 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 {
@@ -5691,10 +5687,6 @@ 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_} {
@@ -5819,8 +5811,8 @@ 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 {};
@@ -6053,10 +6045,6 @@ 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_} {}

diff --git a/tests/std/tests/P2442R1_views_chunk/test.cpp b/tests/std/tests/P2442R1_views_chunk/test.cpp
@@ -35,6 +35,10 @@ 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>);
+
     // Validate borrowed_range
     STATIC_ASSERT(ranges::borrowed_range<R> == (ranges::borrowed_range<V> && forward_range<V>) );
 
@@ -59,6 +63,8 @@ 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(same_as<decltype(views::chunk(as_const(rng), 2)), RC>);
         STATIC_ASSERT(noexcept(views::chunk(as_const(rng), 2)) == is_noexcept);
 
@@ -72,6 +78,8 @@ 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(same_as<decltype(views::chunk(move(rng), 2)), RS>);
         STATIC_ASSERT(noexcept(views::chunk(move(rng), 2)) == is_noexcept);
 

diff --git a/tests/std/tests/P2442R1_views_slide/test.cpp b/tests/std/tests/P2442R1_views_slide/test.cpp
@@ -39,6 +39,9 @@ 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>);
+
     // Validate borrowed_range
     static_assert(ranges::borrowed_range<R> == ranges::borrowed_range<V>);
 
@@ -63,6 +66,8 @@ 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(same_as<decltype(views::slide(as_const(rng), 4)), RC>);
         STATIC_ASSERT(noexcept(views::slide(as_const(rng), 4)) == is_noexcept);
 
@@ -76,6 +81,8 @@ 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(same_as<decltype(views::slide(move(rng), 4)), RS>);
         STATIC_ASSERT(noexcept(views::slide(move(rng), 4)) == is_noexcept);