interp = _PyInterpreterState_GET_UNSAFE(); 

You can add listnode or parser variable to avoid having to write "interp->parser.listnode". But for that, you need to name the structure in pycore_pystate.h.

I'm not quite sure what you mean. The change was specifically to move those variables into the interpreter state rather than stand-alone variables, as they were previously.

I suggest to add parser = &interp->parser; and then use parser instead of interp. Or something similar with listnode.

Ah, OK, I understand now :-)

Not sure what an additional variable buys in this case. I agree, if readability were adversely affected, it would be worth doing. As it is, it seems readable enough.

It was just a minor remark for readability. You're free to ignore it ;-)