TableGen assertion mechanism

Hi all,

I found myself needing some kind of assertion mechanism in TableGen that would error out whenever a precondition isn't met.
This precondition needs to be checked parse-time, as it's much harder to retroactively verify in the backend in my case.

Is there any simple way to achieve this right now?

I think one could simulate this by doing something invalid (e.g. defining two records with the same name) whenever the precondition evaluates to false, but I'm looking for something cleaner.