P2404R3: Move-Only Types For Comparison Concepts

stl/inc/compare

@@ -290,23 +290,26 @@ struct common_comparison_category {
 template <class _Ty, class _Cat>
 concept _Compares_as = same_as<common_comparison_category_t<_Ty, _Cat>, _Cat>;
 
-// clang-format off
 _EXPORT_STD template <class _Ty, class _Cat = partial_ordering>
 concept three_way_comparable = _Half_equality_comparable<_Ty, _Ty> && _Half_ordered<_Ty, _Ty>
-    && requires(const remove_reference_t<_Ty>& __a, const remove_reference_t<_Ty>& __b) {
-        { __a <=> __b } -> _Compares_as<_Cat>;
-    };
+                            && requires(const remove_reference_t<_Ty>& __a, const remove_reference_t<_Ty>& __b) {
+                                   { __a <=> __b } -> _Compares_as<_Cat>;
+                               };
 
 _EXPORT_STD template <class _Ty1, class _Ty2, class _Cat = partial_ordering>
-concept three_way_comparable_with = three_way_comparable<_Ty1, _Cat> && three_way_comparable<_Ty2, _Cat>
+concept three_way_comparable_with =
+    three_way_comparable<_Ty1, _Cat> && three_way_comparable<_Ty2, _Cat>
+#if _HAS_CXX23
+    && _Comparison_common_type_with<_Ty1, _Ty2>
+#else // ^^^ C++23 / C++20 vvv
     && common_reference_with<const remove_reference_t<_Ty1>&, const remove_reference_t<_Ty2>&>
+#endif // C++20
     && three_way_comparable<common_reference_t<const remove_reference_t<_Ty1>&, const remove_reference_t<_Ty2>&>, _Cat>
     && _Weakly_equality_comparable_with<_Ty1, _Ty2> && _Partially_ordered_with<_Ty1, _Ty2>
     && requires(const remove_reference_t<_Ty1>& __t, const remove_reference_t<_Ty2>& __u) {
-        { __t <=> __u } -> _Compares_as<_Cat>;
-        { __u <=> __t } -> _Compares_as<_Cat>;
-    };
-// clang-format on
+           { __t <=> __u } -> _Compares_as<_Cat>;
+           { __u <=> __t } -> _Compares_as<_Cat>;
+       };
 
 _EXPORT_STD template <class _Ty1, class _Ty2 = _Ty1>
 using compare_three_way_result_t =

stl/inc/concepts

@@ -206,9 +206,26 @@ concept _Weakly_equality_comparable_with =
 _EXPORT_STD template <class _Ty>
 concept equality_comparable = _Half_equality_comparable<_Ty, _Ty>;
 
+#if _HAS_CXX23
+template <class _Ty1, class _Ty2, class _Ref = common_reference_t<const _Ty1&, const _Ty2&>>
+concept _Comparison_common_type_with_impl =
+    same_as<_Ref, common_reference_t<const _Ty2&, const _Ty1&>>
+    && requires {
+           requires convertible_to<const _Ty1&, const _Ref&> || convertible_to<_Ty1, const _Ref&>;
+           requires convertible_to<const _Ty2&, const _Ref&> || convertible_to<_Ty2, const _Ref&>;
+       };
+
+template <class _Ty1, class _Ty2>
+concept _Comparison_common_type_with = _Comparison_common_type_with_impl<remove_cvref_t<_Ty1>, remove_cvref_t<_Ty2>>;
+#endif // _HAS_CXX23
+
 _EXPORT_STD template <class _Ty1, class _Ty2>
 concept equality_comparable_with = equality_comparable<_Ty1> && equality_comparable<_Ty2>
+#if _HAS_CXX23
+    && _Comparison_common_type_with<_Ty1, _Ty2>
+#else // ^^^ C++23 / C++20 vvv
     && common_reference_with<const remove_reference_t<_Ty1>&, const remove_reference_t<_Ty2>&>
+#endif // C++20
     && equality_comparable<common_reference_t<const remove_reference_t<_Ty1>&, const remove_reference_t<_Ty2>&>>
     && _Weakly_equality_comparable_with<_Ty1, _Ty2>;
 

stl/inc/yvals_core.h

@@ -333,6 +333,7 @@
 //     (missing views::zip_transform, views::adjacent, and views::adjacent_transform)
 // P2322R6 ranges::fold_left, ranges::fold_right, Etc.
 // P2387R3 Pipe Support For User-Defined Range Adaptors
+// P2404R3 Move-Only Types For Comparison Concepts
 // P2417R2 More constexpr bitset
 // P2438R2 string::substr() &&
 // P2440R1 ranges::iota, ranges::shift_left, ranges::shift_right
@@ -1565,7 +1566,11 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 
 #if _HAS_CXX20
 #if !defined(__EDG__) || defined(__INTELLISENSE__) // TRANSITION, GH-395
-#define __cpp_lib_concepts 202002L
+#if _HAS_CXX23 // TRANSITION, GH-395 - move down to "macros with language mode sensitivity" section
+#define __cpp_lib_concepts 202207L // P2404R3 Move-Only Types For Comparison Concepts
+#else // ^^^ C++23 / C++20 vvv
+#define __cpp_lib_concepts 202002L // P1964R2 Replacing boolean With boolean-testable
+#endif // C++20
 #endif // !defined(__EDG__) || defined(__INTELLISENSE__)
 
 #ifdef __cpp_lib_concepts

tests/libcxx/expected_results.txt

@@ -54,6 +54,16 @@ std/ranges/range.access/end.pass.cpp FAIL
 std/ranges/range.access/rbegin.pass.cpp FAIL
 std/ranges/range.access/rend.pass.cpp FAIL
 
+# libc++ has not implemented P2404R3: "Move-Only Types For Comparison Concepts"
+std/algorithms/alg.sorting/alg.sort/partial.sort.copy/ranges_partial_sort_copy.pass.cpp FAIL
+std/language.support/support.limits/support.limits.general/concepts.version.compile.pass.cpp FAIL
+std/utilities/function.objects/range.cmp/equal_to.pass.cpp FAIL
+std/utilities/function.objects/range.cmp/greater.pass.cpp FAIL
+std/utilities/function.objects/range.cmp/greater_equal.pass.cpp FAIL
+std/utilities/function.objects/range.cmp/less.pass.cpp FAIL
+std/utilities/function.objects/range.cmp/less_equal.pass.cpp FAIL
+std/utilities/function.objects/range.cmp/not_equal_to.pass.cpp FAIL
+
 # Various bogosity (LLVM-D141004)
 std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/construct_pair_const_lvalue_pair.pass.cpp:0 FAIL
 std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/construct_pair_values.pass.cpp:0 FAIL

tests/libcxx/skipped_tests.txt

@@ -54,6 +54,16 @@ ranges\range.access\end.pass.cpp
 ranges\range.access\rbegin.pass.cpp
 ranges\range.access\rend.pass.cpp
 
+# libc++ has not implemented P2404R3: "Move-Only Types For Comparison Concepts"
+algorithms\alg.sorting\alg.sort\partial.sort.copy\ranges_partial_sort_copy.pass.cpp
+language.support\support.limits\support.limits.general\concepts.version.compile.pass.cpp
+utilities\function.objects\range.cmp\equal_to.pass.cpp
+utilities\function.objects\range.cmp\greater.pass.cpp
+utilities\function.objects\range.cmp\greater_equal.pass.cpp
+utilities\function.objects\range.cmp\less.pass.cpp
+utilities\function.objects\range.cmp\less_equal.pass.cpp
+utilities\function.objects\range.cmp\not_equal_to.pass.cpp
+
 # Various bogosity (LLVM-D141004)
 utilities\utility\mem.res\mem.poly.allocator.class\mem.poly.allocator.mem\construct_pair_const_lvalue_pair.pass.cpp
 utilities\utility\mem.res\mem.poly.allocator.class\mem.poly.allocator.mem\construct_pair_values.pass.cpp

tests/std/test.lst

@@ -567,6 +567,7 @@ tests\P2322R6_ranges_alg_fold
 tests\P2387R3_bind_back
 tests\P2387R3_pipe_support_for_user_defined_range_adaptors
 tests\P2401R0_conditional_noexcept_for_exchange
+tests\P2404R3_move_only_types_for_comparison_concepts
 tests\P2408R5_ranges_iterators_to_classic_algorithms
 tests\P2415R2_owning_view
 tests\P2417R2_constexpr_bitset

tests/std/tests/P2404R3_move_only_types_for_comparison_concepts/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\concepts_latest_matrix.lst

tests/std/tests/P2404R3_move_only_types_for_comparison_concepts/test.compile.pass.cpp

@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <compare>
+#include <concepts>
+#include <cstddef>
+#include <memory>
+#include <type_traits>
+
+using namespace std;
+
+struct MoveOnly {
+    MoveOnly(int); // not defined
+    MoveOnly(const MoveOnly&)            = delete;
+    MoveOnly& operator=(const MoveOnly&) = delete;
+    MoveOnly(MoveOnly&&)                 = default;
+    MoveOnly& operator=(MoveOnly&&)      = default;
+
+    strong_ordering operator<=>(const MoveOnly&) const = default;
+    strong_ordering operator<=>(int) const; // not defined
+};
+
+// Check three_way_comparable_with
+static_assert(three_way_comparable_with<MoveOnly, int>);
+static_assert(three_way_comparable_with<int, MoveOnly>);
+static_assert(three_way_comparable_with<MoveOnly, int, strong_ordering>);
+static_assert(three_way_comparable_with<int, MoveOnly, strong_ordering>);
+
+// Check equality_comparable_with
+static_assert(equality_comparable_with<MoveOnly, int>);
+static_assert(equality_comparable_with<int, MoveOnly>);
+static_assert(equality_comparable_with<unique_ptr<int>, nullptr_t>);
+static_assert(equality_comparable_with<nullptr_t, unique_ptr<int>>);
+
+// Check totally_ordered_with
+static_assert(totally_ordered_with<MoveOnly, int>);
+static_assert(totally_ordered_with<int, MoveOnly>);
+
+// Check [diff.cpp20.concepts]
+// clang-format off
+template <class T, class U>
+    requires equality_comparable_with<T, U>
+bool attempted_equals(const T&, const U&); // not defined
+
+template <class T, class U>
+    requires common_reference_with<const remove_reference_t<T>&, const remove_reference_t<U>&>
+bool attempted_equals(const T&, const U&); // not defined
+// clang-format on
+
+template <class T>
+constexpr bool check_diff_cpp20_concepts = !requires(T p) { attempted_equals(p, nullptr); };
+
+static_assert(check_diff_cpp20_concepts<shared_ptr<int>>);
+
+int main() {} // COMPILE-ONLY

tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp

@@ -458,7 +458,15 @@ STATIC_ASSERT(__cpp_lib_clamp == 201603L);
 STATIC_ASSERT(__cpp_lib_complex_udls == 201309L);
 #endif
 
-#if _HAS_CXX20 && !defined(__EDG__) // TRANSITION, GH-395
+#if _HAS_CXX23 && !defined(__EDG__) // TRANSITION, GH-395
+#ifndef __cpp_lib_concepts
+#error __cpp_lib_concepts is not defined
+#elif __cpp_lib_concepts != 202207L
+#error __cpp_lib_concepts is not 202207L
+#else
+STATIC_ASSERT(__cpp_lib_concepts == 202207L);
+#endif
+#elif _HAS_CXX20 && !defined(__EDG__) // TRANSITION, GH-395
 #ifndef __cpp_lib_concepts
 #error __cpp_lib_concepts is not defined
 #elif __cpp_lib_concepts != 202002L