QMetaType: fix QMetaTypes for non-const references

Namely, they shouldn't be supported. Even trying to create such a type
(as in QMetaType::fromType<int &>()) should fail, because for the
purposes of the meta type, they are not the same.

However, they were being registered in the meta objects' meta type list
as a mistake since commit cb43aaca112c864a201b87037692cb8ae2e93b6d
("Introduce QMetaObject::metaType"), including for output parameters in
D-Bus remote objects' meta objects. despite the comment saying "type id
not available".

[ChangeLog][Potentially Source-incompatible Changes] Made meta types for
non-const references fail to compile. Previously, QMetaType::fromType
allowed this to compile, but returned the meta type for the base type,
which was incorrect. Const references are understood to be the same as
the base type.

[ChangeLog][Important Behavior Changes] The meta type for non-const
reference parameters in extracted methods (signals, slots, etc.) is no
longer available in QMetaMethod. This used to be the case in Qt 4.x and
5.x, but due to a mistake in Qt 6.0-6.3, QMetaMethod would incorrectly
report the base (non-reference) type. Additionally, both the reference
and the non-reference types may have been reported in different APIs.

Pick-to: 6.4
Change-Id: I36b24183fbd041179f2ffffd1702384d2b64a5f9
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/dbus/qdbusmetaobject.cpp b/src/dbus/qdbusmetaobject.cpp
index 79372484fb..54c9389862 100644
--- a/src/dbus/qdbusmetaobject.cpp
+++ b/src/dbus/qdbusmetaobject.cpp
@@ -477,8 +477,8 @@ void QDBusMetaObjectGenerator::write(QDBusMetaObject *obj)
                     // Output parameters are references; type id not available
                     typeName = QMetaType(type).name();
                     typeName.append('&');
+                    type = QMetaType::UnknownType;
                 }
-                Q_ASSERT(type != QMetaType::UnknownType);
                 int typeInfo;
                 if (!typeName.isEmpty())
                     typeInfo = IsUnresolvedType | strings.enter(typeName);