[antlr-interest] Followup: labels and return types - multiple elements sharing label name

[Mats Behre]

After thinking a bit more about it, I think the ideal solution would be if all rules not adding any return values got the same return type.
To take it even further, all rules adding the same set of return values could also get one return type (preferably a subclass of the valueless one).
That would probably be more like how it would be hand coded.

Rgds,
Mats