QKeyCombination: move the operators into namespace Qt

QKeyCombination comes with a few operators that combine a Qt::Modifier
and a Qt::Key. These operators are normally defined in Qt's own
namespace (which by default is the global namespace), but indeed the
arguments are declared in the (nested) namespace `Qt`. This is wrong,
as their lookup will fail if a user places an unrelated operator| in
a custom namespace U and then tries to use QKeyCombination's operators:
the overload in namespace U will hide the ones defined globally;
unqualified lookup (as per [over.match.oper]) will search in the
namespaces associated with the parameters (QtNamespace::Qt), but the
operators are *not* in there!

In other words:

namespace NS {
  X operator|(Y, Z);
  auto kc = Qt::Shift | Qt::Key_A;
}

fails to compile if QKeyCombination's operator| is *not* defined in the
`Qt` namespace.

Fix this by indeed defining the operator where it belongs. The functions
are all inline and non-exported so there should not be any ABI issues.

Change-Id: I6d7a4e976fb109b7bf514011142b9a9573e507c5
Pick-to: 6.7 6.5 6.2
Fixes: QTBUG-126820
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 1f77e8566f71d98f4bc6bbf5092594e67a32f268)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/global/qnamespace.h

@@ -1925,6 +1925,7 @@ private:
 
 Q_DECLARE_TYPEINFO(QKeyCombination, Q_RELOCATABLE_TYPE);
 
+namespace Qt {
 constexpr QKeyCombination operator|(Qt::Modifier modifier, Qt::Key key) noexcept
 {
     return QKeyCombination(modifier, key);
@@ -2014,6 +2015,7 @@ constexpr QKeyCombination operator+(Qt::Key key, Qt::KeyboardModifiers modifiers
     return QKeyCombination(modifiers, key);
 }
 #endif
+}
 
 QT_END_NAMESPACE
 

src/corelib/global/qnamespace.qdoc

@@ -3512,10 +3512,10 @@
 */
 
 /*!
-  \fn QKeyCombination operator|(Qt::Modifier modifier, Qt::Key key) noexcept
-  \fn QKeyCombination operator|(Qt::KeyboardModifier modifier, Qt::Key key) noexcept
-  \fn QKeyCombination operator|(Qt::Key key, Qt::Modifier modifier) noexcept
-  \fn QKeyCombination operator|(Qt::Key key, Qt::KeyboardModifier modifier) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::Modifier modifier, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::KeyboardModifier modifier, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::Key key, Qt::Modifier modifier) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::Key key, Qt::KeyboardModifier modifier) noexcept
 
   \relates QKeyCombination
 
@@ -3524,10 +3524,10 @@
 */
 
 /*!
-  \fn QKeyCombination operator|(Qt::Modifiers modifiers, Qt::Key key) noexcept
-  \fn QKeyCombination operator|(Qt::KeyboardModifiers modifiers, Qt::Key key) noexcept
-  \fn QKeyCombination operator|(Qt::Key key, Qt::Modifiers modifiers) noexcept
-  \fn QKeyCombination operator|(Qt::Key key, Qt::KeyboardModifiers modifiers) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::Modifiers modifiers, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::KeyboardModifiers modifiers, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::Key key, Qt::Modifiers modifiers) noexcept
+  \fn QKeyCombination Qt::operator|(Qt::Key key, Qt::KeyboardModifiers modifiers) noexcept
 
   \relates QKeyCombination
 
@@ -3536,10 +3536,10 @@
 */
 
 /*!
-  \fn QKeyCombination operator+(Qt::Modifier modifier, Qt::Key key) noexcept
-  \fn QKeyCombination operator+(Qt::KeyboardModifier modifier, Qt::Key key) noexcept
-  \fn QKeyCombination operator+(Qt::Key key, Qt::Modifier modifier) noexcept
-  \fn QKeyCombination operator+(Qt::Key key, Qt::KeyboardModifier modifier) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::Modifier modifier, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::KeyboardModifier modifier, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::Key key, Qt::Modifier modifier) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::Key key, Qt::KeyboardModifier modifier) noexcept
 
   \relates QKeyCombination
   \deprecated
@@ -3551,10 +3551,10 @@
 */
 
 /*!
-  \fn QKeyCombination operator+(Qt::Modifiers modifiers, Qt::Key key) noexcept
-  \fn QKeyCombination operator+(Qt::KeyboardModifiers modifiers, Qt::Key key) noexcept
-  \fn QKeyCombination operator+(Qt::Key key, Qt::Modifiers modifiers) noexcept
-  \fn QKeyCombination operator+(Qt::Key key, Qt::KeyboardModifiers modifiers) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::Modifiers modifiers, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::KeyboardModifiers modifiers, Qt::Key key) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::Key key, Qt::Modifiers modifiers) noexcept
+  \fn QKeyCombination Qt::operator+(Qt::Key key, Qt::KeyboardModifiers modifiers) noexcept
 
   \relates QKeyCombination
   \deprecated

tests/auto/corelib/global/qkeycombination/tst_qkeycombination.cpp

@@ -274,6 +274,17 @@ void tst_QKeyCombination::operator_or()
     QCOMPARE(Qt::ControlModifier | Qt::Key_Escape, QKeyCombination(Qt::ControlModifier, Qt::Key_Escape));
 }
 
+namespace QTBUG_126820 {
+struct S {};
+S operator|(S, S);
+S operator+(S, S);
+
+[[maybe_unused]] constexpr QKeyCombination kc1 = Qt::SHIFT | Qt::Key_A;
+#if QT_DEPRECATED_SINCE(6, 0)
+[[maybe_unused]] constexpr QKeyCombination kc2 = Qt::SHIFT + Qt::Key_A;
+#endif
+}
+
 QTEST_APPLESS_MAIN(tst_QKeyCombination)
 
 #include "tst_qkeycombination.moc"