QMetaProperty: remove property auto-registration code

Qt 6 automatically registers all types used in properties. Thus, the
functionality is mostly obsolete since Qt 6. We can simply return the
stored metatype's id instead.
The code in moc is kept in place for compatibility with older code,
though there seem to be no remaining users of the metacall in Qt itself
anymore.

Change-Id: I3c654150988ae7780b4e9ea1f16191fdadf8d791
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/kernel/qmetaobject.cpp

@@ -3160,19 +3160,20 @@ bool QMetaProperty::isAlias() const
     return (data.flags() & Alias);
 }
 
+#if QT_DEPRECATED_SINCE(6, 4)
 /*!
     \internal
+    Historically:
     Executes metacall with QMetaObject::RegisterPropertyMetaType flag.
     Returns id of registered type or QMetaType::UnknownType if a type
     could not be registered for any reason.
+    Obsolete since Qt 6
 */
 int QMetaProperty::registerPropertyType() const
 {
-    int registerResult = -1;
-    void *argv[] = { &registerResult };
-    mobj->static_metacall(QMetaObject::RegisterPropertyMetaType, data.index(mobj), argv);
-    return registerResult == -1 ? QMetaType::UnknownType : registerResult;
+    return typeId();
 }
+#endif
 
 QMetaProperty::QMetaProperty(const QMetaObject *mobj, int index)
     : mobj(mobj),

src/corelib/kernel/qmetaobject.h

@@ -332,7 +332,10 @@ public:
     inline const QMetaObject *enclosingMetaObject() const { return mobj; }
 
 private:
+#if QT_DEPRECATED_SINCE(6, 4)
+    QT_DEPRECATED_VERSION_X_6_4("obsolete, simply returns typeId()")
     int registerPropertyType() const;
+#endif
 
     struct Data {
         enum { Size = 5 };

src/tools/moc/generator.cpp

@@ -1040,6 +1040,7 @@ void Generator::generateMetacall()
 }
 
 
+// ### Qt 7 (6.x?): remove
 QMultiMap<QByteArray, int> Generator::automaticPropertyMetaTypesHelper()
 {
     QMultiMap<QByteArray, int> automaticPropertyMetaTypes;