when compiling this binding in direct mode, generated code is rejected by compiler:
```

            required property size sizeProp
            Drag.imageSourceSize: delegate.sizeProp

```

not sure if this binding was not compiled before 6.10 or it just worked.

```

[ 18%] Building CXX object CMakeFiles/test.dir/.rcc/qmlcache/test_main1_qml.cpp.o
.rcc/qmlcache/test_main1_qml.cpp:267:10: error: cannot cast 'QQmlSizeValueType' to its private base class 'QSize'
  267 | s.v2_2 = QQmlSizeValueType(std::move(retrieved));
      |          ^
include/Qt6/QtQml/6.10.0/QtQml/private/qqmlvaluetype_p.h:172:41: note: declared private here
  172 | struct Q_QML_EXPORT QQmlSizeValueType : private QSize
      |                                         ^~~~~~~~~~~~~
1 error generated.

```