Implement LWG-4013 lazy_split_view::outer-iterator::value_type shou…

…ld not provide default constructor (#4530)
microsoft · Mar 28, 2024 · d8f6dc5 · d8f6dc5
1 parent 370f9a9
commit d8f6dc5
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Showing 3 changed files with 24 additions and 3 deletions.
diff --git a/stl/inc/ranges b/stl/inc/ranges
@@ -4706,12 +4706,13 @@ namespace ranges {
             private:
                 /* [[no_unique_address]] */ _Outer_iter _First{};
 
-            public:
-                value_type() = default;
                 constexpr explicit value_type(_Outer_iter _First_) noexcept(
-                    is_nothrow_move_constructible_v<_Outer_iter>) // strengthened
+                    is_nothrow_move_constructible_v<_Outer_iter>)
                     : _First{_STD move(_First_)} {}
 
+                friend _Outer_iter;
+
+            public:
                 _NODISCARD constexpr auto begin() const {
                     return _Inner_iter<_Const>{_First};
                 }

diff --git a/tests/libcxx/expected_results.txt b/tests/libcxx/expected_results.txt
@@ -165,6 +165,10 @@ std/utilities/memory/specialized.algorithms/uninitialized.fill.n/ranges_uninitia
 std/utilities/memory/specialized.algorithms/uninitialized.move/ranges_uninitialized_move.pass.cpp FAIL
 std/utilities/memory/specialized.algorithms/uninitialized.move/ranges_uninitialized_move_n.pass.cpp FAIL
 
+# libc++ doesn't implement LWG-4013
+std/ranges/range.adaptors/range.lazy.split/range.lazy.split.outer.value/ctor.default.pass.cpp FAIL
+std/ranges/range.adaptors/range.lazy.split/range.lazy.split.outer.value/ctor.iter.pass.cpp FAIL
+
 # If any feature-test macro test is failing, this consolidated test will also fail.
 std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp FAIL
 

diff --git a/tests/std/tests/P0896R4_views_lazy_split/test.cpp b/tests/std/tests/P0896R4_views_lazy_split/test.cpp
@@ -63,6 +63,10 @@ constexpr void test_one(Base&& base, Delimiter&& delimiter, Expected&& expected)
 
         STATIC_ASSERT(same_as<decltype(base | closure), R>);
         STATIC_ASSERT(noexcept(base | closure) == is_noexcept);
+
+        using outer_iterator = decltype(views::lazy_split(base, delimiter).begin());
+        STATIC_ASSERT(!is_default_constructible_v<iter_value_t<outer_iterator>>); // LWG-4013
+        STATIC_ASSERT(!is_constructible_v<iter_value_t<outer_iterator>, outer_iterator>); // LWG-4013
     }
 
     // ... with const lvalue argument
@@ -77,6 +81,10 @@ constexpr void test_one(Base&& base, Delimiter&& delimiter, Expected&& expected)
 
         STATIC_ASSERT(same_as<decltype(as_const(base) | closure), R>);
         STATIC_ASSERT(noexcept(as_const(base) | closure) == is_noexcept);
+
+        using outer_iterator = decltype(views::lazy_split(as_const(base), delimiter).begin());
+        STATIC_ASSERT(!is_default_constructible_v<iter_value_t<outer_iterator>>); // LWG-4013
+        STATIC_ASSERT(!is_constructible_v<iter_value_t<outer_iterator>, outer_iterator>); // LWG-4013
     } else if constexpr (!is_view) {
         using LSV                  = ranges::lazy_split_view<ranges::ref_view<const remove_reference_t<Base>>, DV>;
         constexpr bool is_noexcept = is_nothrow_constructible_v<LSV, const remove_reference_t<Base>&, Delimiter&>;
@@ -99,6 +107,10 @@ constexpr void test_one(Base&& base, Delimiter&& delimiter, Expected&& expected)
 
         STATIC_ASSERT(same_as<decltype(move(base) | closure), R>);
         STATIC_ASSERT(noexcept(move(base) | closure) == is_noexcept);
+
+        using outer_iterator = decltype(views::lazy_split(move(base), delimiter).begin());
+        STATIC_ASSERT(!is_default_constructible_v<iter_value_t<outer_iterator>>); // LWG-4013
+        STATIC_ASSERT(!is_constructible_v<iter_value_t<outer_iterator>, outer_iterator>); // LWG-4013
     } else if constexpr (movable<remove_reference_t<Base>>) {
         using RS = ranges::lazy_split_view<ranges::owning_view<remove_reference_t<Base>>, DV>;
         constexpr bool is_noexcept =
@@ -123,6 +135,10 @@ constexpr void test_one(Base&& base, Delimiter&& delimiter, Expected&& expected)
 
         STATIC_ASSERT(same_as<decltype(move(as_const(base)) | closure), R>);
         STATIC_ASSERT(noexcept(move(as_const(base)) | closure) == is_noexcept);
+
+        using outer_iterator = decltype(views::lazy_split(move(as_const(base)), delimiter).begin());
+        STATIC_ASSERT(!is_default_constructible_v<iter_value_t<outer_iterator>>); // LWG-4013
+        STATIC_ASSERT(!is_constructible_v<iter_value_t<outer_iterator>, outer_iterator>); // LWG-4013
     }
 
     // Validate deduction guide