4thline/cling — pull request #70 by lynxis (2013-06-24 00:19:33+00:00)
Title: Service->Action->Argument: Ignore <retval/> if Direction of Argument is IN

This is only for the Interpretation of Action.
It will still report an Error within Validation of Meta/ActionArgument Class.

Maybe it is cleaner to first validate ActionArgument there and reset retval there.