QProperty: Cleanup QPropertyAlias leftovers

This removes traces of QPropertyAlias which is internal API which is
a) not really working even before this change (no compatibility with
   QBindableInterface due to QPropertyAlias not being derived from
   QUntypedPropertyData)
b) not used anywhere

For BIC reasons, we need to keep some methods still around until Qt 7,
though.

Change-Id: I5bb4735a4c88cba275dc2cc6e29a46ca09622059
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

3 files changed, 4 insertions, 21 deletions

diff --git a/src/corelib/kernel/qproperty.cpp b/src/corelib/kernel/qproperty.cpp
index a1b2f83c5b..d8176a845a 100644
--- a/src/corelib/kernel/qproperty.cpp
+++ b/src/corelib/kernel/qproperty.cpp
@@ -571,10 +571,9 @@ QPropertyObserver::QPropertyObserver(ChangeHandler changeHandler)
     d.setChangeHandler(changeHandler);
 }
 
-QPropertyObserver::QPropertyObserver(QUntypedPropertyData *aliasedPropertyPtr)
+QPropertyObserver::QPropertyObserver(QUntypedPropertyData *)
 {
-    QPropertyObserverPointer d{this};
-    d.setAliasedProperty(aliasedPropertyPtr);
+    // ### Qt 7: Remove, currently left for binary compatibility
 }
 
 /*! \internal
@@ -625,8 +624,6 @@ QPropertyObserver &QPropertyObserver::operator=(QPropertyObserver &&other) noexc
 
 void QPropertyObserverPointer::unlink()
 {
-    if (ptr->next.tag() == QPropertyObserver::ObserverNotifiesAlias)
-        ptr->aliasedPropertyData = nullptr;
     if (ptr->next)
         ptr->next->prev = ptr->prev;
     if (ptr->prev)
@@ -642,13 +639,6 @@ void QPropertyObserverPointer::setChangeHandler(QPropertyObserver::ChangeHandler
     ptr->next.setTag(QPropertyObserver::ObserverNotifiesChangeHandler);
 }
 
-void QPropertyObserverPointer::setAliasedProperty(QUntypedPropertyData *property)
-{
-    Q_ASSERT(ptr->next.tag() != QPropertyObserver::ObserverIsPlaceholder);
-    ptr->aliasedPropertyData = property;
-    ptr->next.setTag(QPropertyObserver::ObserverNotifiesAlias);
-}
-
 void QPropertyObserverPointer::setBindingToNotify(QPropertyBindingPrivate *binding)
 {
     Q_ASSERT(ptr->next.tag() != QPropertyObserver::ObserverIsPlaceholder);
@@ -708,9 +698,6 @@ void QPropertyObserverPointer::notify(QUntypedPropertyData *propertyDataPtr)
      */
     while (observer) {
         QPropertyObserver *next = observer->next.data();
-
-        char preventBug[1] = {'\0'}; // QTBUG-87245
-        Q_UNUSED(preventBug);
         switch (QPropertyObserver::ObserverTag(observer->next.tag())) {
         case QPropertyObserver::ObserverNotifiesChangeHandler:
         {
@@ -734,11 +721,10 @@ void QPropertyObserverPointer::notify(QUntypedPropertyData *propertyDataPtr)
             next = protector.next();
             break;
         }
-        case QPropertyObserver::ObserverNotifiesAlias:
-            break;
         case QPropertyObserver::ObserverIsPlaceholder:
             // recursion is already properly handled somewhere else
             break;
+        default: Q_UNREACHABLE();
         }
         observer = next;
     }
diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index f5513be73f..a2c2875a12 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -215,7 +215,6 @@ public:
     enum ObserverTag {
         ObserverNotifiesBinding, // observer was installed to notify bindings that obsverved property changed
         ObserverNotifiesChangeHandler, // observer is a change handler, which runs on every change
-        ObserverNotifiesAlias, // used for QPropertyAlias
         ObserverIsPlaceholder  // the observer before this one is currently evaluated in QPropertyObserver::notifyObservers.
     };
 protected:
@@ -237,7 +236,6 @@ private:
     union {
         QPropertyBindingPrivate *binding = nullptr;
         ChangeHandler changeHandler;
-        QUntypedPropertyData *aliasedPropertyData;
     };
 };
 
@@ -260,7 +258,7 @@ protected:
 
     QUntypedPropertyData *aliasedProperty() const
     {
-        return aliasedPropertyData;
+        return nullptr;
     }
 
 private:
diff --git a/src/corelib/kernel/qproperty_p.h b/src/corelib/kernel/qproperty_p.h
index d00094c54f..32ff31166c 100644
--- a/src/corelib/kernel/qproperty_p.h
+++ b/src/corelib/kernel/qproperty_p.h
@@ -105,7 +105,6 @@ struct QPropertyObserverPointer
 
     void setBindingToNotify(QPropertyBindingPrivate *binding);
     void setChangeHandler(QPropertyObserver::ChangeHandler changeHandler);
-    void setAliasedProperty(QUntypedPropertyData *propertyPtr);
 
     void notify(QUntypedPropertyData *propertyDataPtr);
 #ifndef QT_NO_DEBUG