Implement P2520R0: move_iterator<T*> should be a random access iter…

…ator
microsoft · Jul 27, 2022 · 363bf89 · 363bf89
1 parent 04ee878
commit 363bf89
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Showing 4 changed files with 39 additions and 21 deletions.
diff --git a/stl/inc/xutility b/stl/inc/xutility
@@ -3186,11 +3186,26 @@ class move_sentinel;
 
 template <class>
 struct _Move_iterator_category {};
+template <class _Iter>
+struct _Move_iterator_concept {
+    using iterator_concept = decltype(_Get_concept());
+    static auto _Get_concept() {
+        if constexpr (_RANGES random_access_iterator<_Iter>) {
+            return random_access_iterator_tag{};
+        } else if constexpr (_RANGES bidirectional_iterator<_Iter>) {
+            return bidirectional_iterator_tag{};
+        } else if constexpr (_RANGES forward_iterator_tag<_Iter>) {
+            return forward_iterator_tag{};
+        } else {
+            return input_iterator_tag{};
+        }
+    }
+};
 
 // clang-format off
 template <class _Iter>
     requires requires { typename _Iter_cat_t<_Iter>; }
-struct _Move_iterator_category<_Iter> {
+struct _Move_iterator_category<_Iter> : _Move_iterator_concept<_Iter> {
     using iterator_category = conditional_t<derived_from<_Iter_cat_t<_Iter>, random_access_iterator_tag>,
         random_access_iterator_tag, _Iter_cat_t<_Iter>>;
 };
@@ -3211,8 +3226,7 @@ public:
     using pointer         = _Iter;
 
 #ifdef __cpp_lib_concepts
-    using iterator_concept = input_iterator_tag;
-    using reference        = iter_rvalue_reference_t<_Iter>;
+    using reference = iter_rvalue_reference_t<_Iter>;
 #else // ^^^ __cpp_lib_concepts / !__cpp_lib_concepts vvv
     using reference =
         conditional_t<is_reference_v<_Iter_ref_t<_Iter>>, remove_reference_t<_Iter_ref_t<_Iter>>&&, _Iter_ref_t<_Iter>>;

diff --git a/stl/inc/yvals_core.h b/stl/inc/yvals_core.h
@@ -273,6 +273,7 @@
 // P2415R2 What Is A view?
 // P2418R2 Add Support For std::generator-like Types To std::format
 // P2432R1 Fix istream_view
+// P2520R0 move_iterator<T*> Should Be A Random-Access Iterator
 
 // _HAS_CXX20 indirectly controls:
 // P0619R4 Removing C++17-Deprecated Features
@@ -1409,6 +1410,7 @@
 #define __cpp_lib_latch                   201907L
 #define __cpp_lib_list_remove_return_type 201806L
 #define __cpp_lib_math_constants          201907L
+#define __cpp_lib_move_iterator_concept   202207L
 #define __cpp_lib_polymorphic_allocator   201902L
 
 #if defined(__cpp_lib_concepts) // TRANSITION, GH-395

diff --git a/tests/std/tests/GH_002581_common_reference_workaround/test.compile.pass.cpp b/tests/std/tests/GH_002581_common_reference_workaround/test.compile.pass.cpp
@@ -27,19 +27,19 @@ static_assert(contiguous_iterator<int Test::*volatile*>);
 static_assert(contiguous_iterator<int Test::*const volatile*>);
 
 // Tests for move_iterator specializations
-static_assert(input_iterator<move_iterator<volatile int*>>);
-static_assert(input_iterator<move_iterator<const volatile int*>>);
-static_assert(input_iterator<move_iterator<volatile double*>>);
-static_assert(input_iterator<move_iterator<const volatile double*>>);
-static_assert(input_iterator<move_iterator<volatile nullptr_t*>>);
-static_assert(input_iterator<move_iterator<const volatile nullptr_t*>>);
-static_assert(input_iterator<move_iterator<volatile Unscoped*>>);
-static_assert(input_iterator<move_iterator<const volatile Unscoped*>>);
-static_assert(input_iterator<move_iterator<volatile Scoped*>>);
-static_assert(input_iterator<move_iterator<const volatile Scoped*>>);
-static_assert(input_iterator<move_iterator<Test* volatile*>>);
-static_assert(input_iterator<move_iterator<Test* const volatile*>>);
-static_assert(input_iterator<move_iterator<int Test::*volatile*>>);
-static_assert(input_iterator<move_iterator<int Test::*const volatile*>>);
+static_assert(random_access_iterator<move_iterator<volatile int*>>);
+static_assert(random_access_iterator<move_iterator<const volatile int*>>);
+static_assert(random_access_iterator<move_iterator<volatile double*>>);
+static_assert(random_access_iterator<move_iterator<const volatile double*>>);
+static_assert(random_access_iterator<move_iterator<volatile nullptr_t*>>);
+static_assert(random_access_iterator<move_iterator<const volatile nullptr_t*>>);
+static_assert(random_access_iterator<move_iterator<volatile Unscoped*>>);
+static_assert(random_access_iterator<move_iterator<const volatile Unscoped*>>);
+static_assert(random_access_iterator<move_iterator<volatile Scoped*>>);
+static_assert(random_access_iterator<move_iterator<const volatile Scoped*>>);
+static_assert(random_access_iterator<move_iterator<Test* volatile*>>);
+static_assert(random_access_iterator<move_iterator<Test* const volatile*>>);
+static_assert(random_access_iterator<move_iterator<int Test::*volatile*>>);
+static_assert(random_access_iterator<move_iterator<int Test::*const volatile*>>);
 
 int main() {} // COMPILE-ONLY
diff --git a/tests/std/tests/P0896R4_ranges_iterator_machinery/test.cpp b/tests/std/tests/P0896R4_ranges_iterator_machinery/test.cpp
@@ -3271,17 +3271,19 @@ struct std::common_type<move_iterator_test::input_iter<true>::rvalue_reference,
 
 namespace move_iterator_test {
     // Validate the iterator_concept/iterator_category metaprogramming
-    STATIC_ASSERT(same_as<move_iterator<simple_contiguous_iter<>>::iterator_concept, input_iterator_tag>);
+    STATIC_ASSERT(same_as<move_iterator<simple_contiguous_iter<>>::iterator_concept, random_access_iterator_tag>);
     STATIC_ASSERT(same_as<move_iterator<simple_contiguous_iter<>>::iterator_category, random_access_iterator_tag>);
-    STATIC_ASSERT(same_as<move_iterator<simple_random_iter<>>::iterator_concept, input_iterator_tag>);
+    STATIC_ASSERT(same_as<move_iterator<simple_random_iter<>>::iterator_concept, random_access_iterator_tag>);
     STATIC_ASSERT(same_as<move_iterator<simple_random_iter<>>::iterator_category, random_access_iterator_tag>);
-    STATIC_ASSERT(same_as<move_iterator<simple_bidi_iter<>>::iterator_concept, input_iterator_tag>);
+    STATIC_ASSERT(same_as<move_iterator<simple_bidi_iter<>>::iterator_concept, bidirectional_iterator_tag>);
     STATIC_ASSERT(same_as<move_iterator<simple_bidi_iter<>>::iterator_category, bidirectional_iterator_tag>);
-    STATIC_ASSERT(same_as<move_iterator<simple_forward_iter<>>::iterator_concept, input_iterator_tag>);
+    STATIC_ASSERT(same_as<move_iterator<simple_forward_iter<>>::iterator_concept, forward_iterator_tag>);
     STATIC_ASSERT(same_as<move_iterator<simple_forward_iter<>>::iterator_category, forward_iterator_tag>);
     STATIC_ASSERT(same_as<move_iterator<simple_input_iter>::iterator_concept, input_iterator_tag>);
     STATIC_ASSERT(same_as<move_iterator<simple_input_iter>::iterator_category, input_iterator_tag>);
+    STATIC_ASSERT(same_as<move_iterator<input_iter<true>>::iterator_concept, input_iterator_tag>);
     STATIC_ASSERT(!has_member_iter_category<move_iterator<input_iter<true>>>);
+    STATIC_ASSERT(same_as<move_iterator<input_iter<true>>::iterator_concept, input_iterator_tag>);
     STATIC_ASSERT(!has_member_iter_category<move_iterator<input_iter<false>>>);
 
     // Validate that move_iterator<some_proxy_iterator>::reference is iter_rvalue_reference_t<some_proxy_iterator>