We are currently able to use simple types, i.e. everything that in qt_type_lib in properties, signals and slots (as well as build-in Rust types). We also want to be able to return complex types for properties, slots and signals.

At the very minimum, this should be a QObject* which properties/functions can then be called from QML side.

However, this would limit qmllint (type checking, autocomplete) substantially as it could not interfere the correct type. Therefore it would be great to be able to use all QObject-derived types in properties, signals and slots. In our Rust world, this would mean that we can use all types created with ifaces (#[qobject_impl(Base = ...)]).