That's pretty cool! From what I can tell, it does a morphological guess based on the suffix. If you didn't have the apostrophe, it'd have issues with ambiguity (say "aşı", does it mean vaccine or does it mean "aş" in accusative case?) but the apostrophe solves that problem too.

My solution for this problem in Kip was to go all the way with the morphological analysis using TRmorph (https://github.com/coltekin/TRmorph) for it, and then resolve the ambiguities in type checking / elaboration. (Therefore Kip almost never needs apostrophes.) Whether it was worth it, I don't know, but it was a fun problem to solve. :)