Groovy bug - Stackoverflow calling super methods

I recently stumbled upon a bug in the version of Groovy that I was working with (Groovy 2.1.5), it's a strange one, that seems to have been solved in Groovy 2.2 but I thought I would post it here in case it was useful to anyone else.

The problem is demonstrated in the code below, but the exact use case seems to be having an inheritance structure > 2 classes deep, whereby the method return type changes.

The result in running the above code in Groovy 2.1.5 is a StackOverflow - it seems as though Groovy just recursively calls the doStuff() method on Child class until it errors rather than calling the method on the parent class.  Running on Groovy 2.2.0+ appears to run correctly.

I posted the question on, and it was suggested that it was maybe related to this bug, which has a very re-assuring resolution comment:

looks like the issue was fixed somewhen between 2.2.2 and 2.3.0