Modify the python grammar and matching to the correct error message?

I’m memorializing here (and also asking) because IMHO , the discussion on the python discord #esoteric-python is ephemeral. Anyo suggestions for troubleshooting the mapping of error messages to grammar? …currently the grammar does not disallow yield *() or *() but the compiler (correctly) does disallow. Yesterday, @encukou and I (well, mostly him) ran into: First try at disallowing `yield *()` & `del *()` at the grammar level · encukou/cpython@885aaf8 · GitHub we wanted to add something l...