From ef8fc89355bba8aa97abe9385e4023a0dcb2b318 Mon Sep 17 00:00:00 2001
From: Ivan Solovev <ivan.solovev@qt.io>
Date: Tue, 1 Oct 2024 15:28:35 +0200
Subject: [PATCH] Move CompareThreeWayTester to qcomparehelpers.h

We will need these checks in the qcomparehelpers.h header, so move
the code there.

As a drive-by, use QtOrderingPrivate namespace instead of QtPrivate,
and also mark the constexpr bool variables as inline.

This is required for the follow-up patches.

Task-number: QTBUG-127095
Task-number: QTBUG-120305
Change-Id: I1ea827ecf68b6bffa347dae22ddac25c059b53a9
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit 678e9f614bc5a05d2ff16cf916397998e7cdfca1)
---
 src/corelib/global/qcompare.h        | 47 ++++------------------------
 src/corelib/global/qcomparehelpers.h | 36 +++++++++++++++++++++
 2 files changed, 42 insertions(+), 41 deletions(-)

diff --git a/src/corelib/global/qcompare.h b/src/corelib/global/qcompare.h
index fd9fb84c6b9..7fbf9aabcb3 100644
--- a/src/corelib/global/qcompare.h
+++ b/src/corelib/global/qcompare.h
@@ -629,42 +629,6 @@ QT_BEGIN_INCLUDE_NAMESPACE
 
 QT_END_INCLUDE_NAMESPACE
 
-namespace QtPrivate {
-
-namespace CompareThreeWayTester {
-
-    using Qt::compareThreeWay;
-
-    // Check if compareThreeWay is implemented for the (LT, RT) argument
-    // pair.
-    template <typename LT, typename RT, typename = void>
-    constexpr bool hasCompareThreeWay = false;
-
-    template <typename LT, typename RT>
-    constexpr bool hasCompareThreeWay<
-            LT, RT, std::void_t<decltype(compareThreeWay(std::declval<LT>(), std::declval<RT>()))>
-    > = true;
-
-    // Check if the operation is noexcept. We have two different overloads,
-    // depending on the available compareThreeWay() implementation.
-    // Both are declared, but not implemented. To be used only in unevaluated
-    // context.
-
-    template <typename LT, typename RT,
-             std::enable_if_t<hasCompareThreeWay<LT, RT>, bool> = true>
-    constexpr bool compareThreeWayNoexcept() noexcept
-    { return noexcept(compareThreeWay(std::declval<LT>(), std::declval<RT>())); }
-
-    template <typename LT, typename RT,
-             std::enable_if_t<!hasCompareThreeWay<LT, RT> && hasCompareThreeWay<RT, LT>,
-                              bool> = true>
-    constexpr bool compareThreeWayNoexcept() noexcept
-    { return noexcept(compareThreeWay(std::declval<RT>(), std::declval<LT>())); }
-
-} // namespace CompareThreeWayTester
-
-} // namespace QtPrivate
-
 #if defined(Q_QDOC)
 
 template <typename LeftType, typename RightType>
@@ -673,14 +637,15 @@ auto qCompareThreeWay(const LeftType &lhs, const RightType &rhs);
 #else
 
 template <typename LT, typename RT,
-          std::enable_if_t<QtPrivate::CompareThreeWayTester::hasCompareThreeWay<LT, RT>
-                            || QtPrivate::CompareThreeWayTester::hasCompareThreeWay<RT, LT>,
-                           bool> = true>
+          std::enable_if_t<
+                  QtOrderingPrivate::CompareThreeWayTester::hasCompareThreeWay<LT, RT>
+                    || QtOrderingPrivate::CompareThreeWayTester::hasCompareThreeWay<RT, LT>,
+                  bool> = true>
 auto qCompareThreeWay(const LT &lhs, const RT &rhs)
-        noexcept(QtPrivate::CompareThreeWayTester::compareThreeWayNoexcept<LT, RT>())
+        noexcept(QtOrderingPrivate::CompareThreeWayTester::compareThreeWayNoexcept<LT, RT>())
 {
     using Qt::compareThreeWay;
-    if constexpr (QtPrivate::CompareThreeWayTester::hasCompareThreeWay<LT, RT>) {
+    if constexpr (QtOrderingPrivate::CompareThreeWayTester::hasCompareThreeWay<LT, RT>) {
         return compareThreeWay(lhs, rhs);
     } else {
         const auto retval = compareThreeWay(rhs, lhs);
diff --git a/src/corelib/global/qcomparehelpers.h b/src/corelib/global/qcomparehelpers.h
index 8bf78d766bc..dcaa886bcdd 100644
--- a/src/corelib/global/qcomparehelpers.h
+++ b/src/corelib/global/qcomparehelpers.h
@@ -864,6 +864,42 @@ compareThreeWay(std::nullptr_t lhs, Qt::totally_ordered_wrapper<T*> rhs) noexcep
 template <typename P>
 class QTypeInfo<Qt::totally_ordered_wrapper<P>> : public QTypeInfo<P> {};
 
+namespace QtOrderingPrivate {
+
+namespace CompareThreeWayTester {
+
+using Qt::compareThreeWay;
+
+// Check if compareThreeWay is implemented for the (LT, RT) argument
+// pair.
+template <typename LT, typename RT, typename = void>
+constexpr inline bool hasCompareThreeWay = false;
+
+template <typename LT, typename RT>
+constexpr inline bool hasCompareThreeWay<
+        LT, RT, std::void_t<decltype(compareThreeWay(std::declval<LT>(), std::declval<RT>()))>
+    > = true;
+
+// Check if the operation is noexcept. We have two different overloads,
+// depending on the available compareThreeWay() implementation.
+// Both are declared, but not implemented. To be used only in unevaluated
+// context.
+
+template <typename LT, typename RT,
+          std::enable_if_t<hasCompareThreeWay<LT, RT>, bool> = true>
+constexpr bool compareThreeWayNoexcept() noexcept
+{ return noexcept(compareThreeWay(std::declval<LT>(), std::declval<RT>())); }
+
+template <typename LT, typename RT,
+          std::enable_if_t<!hasCompareThreeWay<LT, RT> && hasCompareThreeWay<RT, LT>,
+                           bool> = true>
+constexpr bool compareThreeWayNoexcept() noexcept
+{ return noexcept(compareThreeWay(std::declval<RT>(), std::declval<LT>())); }
+
+} // namespace CompareThreeWayTester
+
+} // namespace QtOrderingPrivate
+
 QT_END_NAMESPACE
 
 namespace std {