Method getThis has incompatible type

[froth30]

After recent revisions, it looks like test class Broadcast is no longer allowing me to initialize devices using a cyclic style of calling setter methods:
device = new SomeConcreteDevice.Builder(...)
.productCode(...)
.serialNumber(...)
.connectors(...)
.build()

This must mean that my getThis method is not properly retaining its usability from its definition in AbstractDevice. So, instead of returning type T, it ends up returning type Nothing in concrete device classes such as Hub, SisterPrinter, CannonPrinter, and GoAmateur.

[froth30]

After redefining all concrete device classes with type parameters and overriding getThis, it appears that everything has been cleared up.