[gcc(refs/users/guojiufu/heads/guojiufu-branch)] libstdc++: Simplify std::totally_ordered (LWG 3331)

[Jiu Fu Guo]

https://gcc.gnu.org/g:0294dc5f4eec5a07d70fac48f75c498c3b1a339b

commit 0294dc5f4eec5a07d70fac48f75c498c3b1a339b
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Feb 19 21:40:03 2020 +0000

    libstdc++: Simplify std::totally_ordered (LWG 3331)
    
            * include/std/concepts (__detail::__partially_ordered_with): Move here
            from <compare>.
            (totally_ordered, totally_ordered_with): Use __partially_ordered_with
            to simplify definition (LWG 3331).
            * libsupc++/compare (__detail::__partially_ordered_with): Move to
            <concepts>.

Diff:
---
 libstdc++-v3/ChangeLog            |  7 +++++++
 libstdc++-v3/include/std/concepts | 35 +++++++++++++++++++----------------
 libstdc++-v3/libsupc++/compare    | 14 --------------
 3 files changed, 26 insertions(+), 30 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 3941bcbe7ba..1711a359256 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,12 @@
 2020-02-19  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/std/concepts (__detail::__partially_ordered_with): Move here
+	from <compare>.
+	(totally_ordered, totally_ordered_with): Use __partially_ordered_with
+	to simplify definition (LWG 3331).
+	* libsupc++/compare (__detail::__partially_ordered_with): Move to
+	<concepts>.
+
 	* include/std/concepts (totally_ordered_with): Remove redundant
 	requirement (LWG 3329).
 
diff --git a/libstdc++-v3/include/std/concepts b/libstdc++-v3/include/std/concepts
index be125c636a1..ba232e953ec 100644
--- a/libstdc++-v3/include/std/concepts
+++ b/libstdc++-v3/include/std/concepts
@@ -297,16 +297,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 						__detail::__cref<_Up>>>
       && __detail::__weakly_eq_cmp_with<_Tp, _Up>;
 
+  namespace __detail
+  {
+    template<typename _Tp, typename _Up>
+      concept __partially_ordered_with
+	= requires(const remove_reference_t<_Tp>& __t,
+		   const remove_reference_t<_Up>& __u) {
+	  { __t <  __u } -> __boolean_testable;
+	  { __t >  __u } -> __boolean_testable;
+	  { __t <= __u } -> __boolean_testable;
+	  { __t >= __u } -> __boolean_testable;
+	  { __u <  __t } -> __boolean_testable;
+	  { __u >  __t } -> __boolean_testable;
+	  { __u <= __t } -> __boolean_testable;
+	  { __u >= __t } -> __boolean_testable;
+	};
+  } // namespace __detail
+
   // [concept.totallyordered], concept totally_ordered
   template<typename _Tp>
     concept totally_ordered
       = equality_comparable<_Tp>
-      && requires(__detail::__cref<_Tp> __a, __detail::__cref<_Tp> __b) {
-	{ __a <  __b } -> __detail::__boolean_testable;
-	{ __a >  __b } -> __detail::__boolean_testable;
-	{ __a <= __b } -> __detail::__boolean_testable;
-	{ __a >= __b } -> __detail::__boolean_testable;
-      };
+      && __detail::__partially_ordered_with<_Tp, _Tp>;
 
   template<typename _Tp, typename _Up>
     concept totally_ordered_with
@@ -314,16 +326,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       && equality_comparable_with<_Tp, _Up>
       && totally_ordered<common_reference_t<__detail::__cref<_Tp>,
 					    __detail::__cref<_Up>>>
-      && requires(__detail::__cref<_Tp> __t, __detail::__cref<_Up> __u) {
-	{ __t <  __u } -> __detail::__boolean_testable;
-	{ __t >  __u } -> __detail::__boolean_testable;
-	{ __t <= __u } -> __detail::__boolean_testable;
-	{ __t >= __u } -> __detail::__boolean_testable;
-	{ __u <  __t } -> __detail::__boolean_testable;
-	{ __u >  __t } -> __detail::__boolean_testable;
-	{ __u <= __t } -> __detail::__boolean_testable;
-	{ __u >= __t } -> __detail::__boolean_testable;
-      };
+      && __detail::__partially_ordered_with<_Tp, _Up>;
 
   template<typename _Tp>
     concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
index ba7db316486..a74ebc845bf 100644
--- a/libstdc++-v3/libsupc++/compare
+++ b/libstdc++-v3/libsupc++/compare
@@ -411,20 +411,6 @@ namespace std
     template<typename _Tp, typename _Cat>
       concept __compares_as
 	= same_as<common_comparison_category_t<_Tp, _Cat>, _Cat>;
-
-    template<typename _Tp, typename _Up>
-      concept __partially_ordered_with
-	= requires(const remove_reference_t<_Tp>& __t,
-		   const remove_reference_t<_Up>& __u) {
-	  { __t <  __u } -> __boolean_testable;
-	  { __t >  __u } -> __boolean_testable;
-	  { __t <= __u } -> __boolean_testable;
-	  { __t >= __u } -> __boolean_testable;
-	  { __u <  __t } -> __boolean_testable;
-	  { __u >  __t } -> __boolean_testable;
-	  { __u <= __t } -> __boolean_testable;
-	  { __u >= __t } -> __boolean_testable;
-	};
   } // namespace __detail
 
   // [cmp.concept], concept three_way_comparable