From 3a8a8b42909f13a3130d9154363fa0e83cdc0957 Mon Sep 17 00:00:00 2001
From: Ivan Solovev <ivan.solovev@qt.io>
Date: Wed, 4 Dec 2024 13:17:51 +0100
Subject: [PATCH] DRY QList and QVLA operator<=>() implementation

Both QList and QVLA defined an if_has_op_less_or_op_compare_three_way
trait. The only difference was that QList's implementation was using
QTypeTraits::has_operator_less_than_container<>, and thus required a
Container template parameter, while QVLA didn't need it.

However, QVLA would still work properly with the _container version
of the trait, so move the QList's implementation into
QtOrderingPrivate and use it consistently in both classes.

Task-number: QTBUG-120305
Change-Id: I1e4415ae5a25d4faad218bbad979a49ce851d557
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
---
 src/corelib/global/qcomparehelpers.h |  7 +++++++
 src/corelib/tools/qlist.h            | 10 ++--------
 src/corelib/tools/qvarlengtharray.h  |  9 +--------
 3 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/src/corelib/global/qcomparehelpers.h b/src/corelib/global/qcomparehelpers.h
index 8ce91229b7f..ede96a83cf6 100644
--- a/src/corelib/global/qcomparehelpers.h
+++ b/src/corelib/global/qcomparehelpers.h
@@ -1250,6 +1250,13 @@ constexpr bool compareThreeWayNoexcept() noexcept
         }
     }
 } synthThreeWay;
+
+template <typename Container, typename T>
+using if_has_op_less_or_op_compare_three_way =
+        std::enable_if_t<
+                std::disjunction_v<QTypeTraits::has_operator_less_than_container<Container, T>,
+                                   QTypeTraits::has_operator_compare_three_way<T>>,
+                bool>;
 #endif // __cpp_lib_three_way_comparison
 
 // These checks do not use Qt::compareThreeWay(), so only work for user-defined
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 8ccf512389d..45ecac01574 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -349,14 +349,8 @@ private:
     }
 
 #if defined(__cpp_lib_three_way_comparison) && defined(__cpp_lib_concepts)
-    template <typename Container, typename U = T>
-    using if_has_op_less_or_op_compare_three_way =
-            std::enable_if_t<
-                std::disjunction_v<QTypeTraits::has_operator_less_than_container<Container, U>,
-                                   QTypeTraits::has_operator_compare_three_way<U>>,
-            bool>;
-
-    template <typename U = T, if_has_op_less_or_op_compare_three_way<QList, U> = true>
+    template <typename U = T,
+              QtOrderingPrivate::if_has_op_less_or_op_compare_three_way<QList, U> = true>
     friend auto operator<=>(const QList &lhs, const QList &rhs)
     {
         return std::lexicographical_compare_three_way(lhs.begin(), lhs.end(),
diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index fb3c53c49cd..cb148075e3f 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -640,15 +640,8 @@ private:
     }
 
 #if defined(__cpp_lib_three_way_comparison) && defined(__cpp_lib_concepts)
-    template <typename U = T>
-    using if_has_op_less_or_op_compare_three_way =
-            std::enable_if_t<
-                std::disjunction_v<QTypeTraits::has_operator_less_than<U>,
-                                   QTypeTraits::has_operator_compare_three_way<U>>,
-            bool>;
-
     template <typename U = T, qsizetype Prealloc2 = Prealloc,
-              if_has_op_less_or_op_compare_three_way<U> = true>
+              QtOrderingPrivate::if_has_op_less_or_op_compare_three_way<QVarLengthArray, U> = true>
     friend auto
     operator<=>(const QVarLengthArray &lhs, const QVarLengthArray<T, Prealloc2> &rhs)
     {