FWIW I separated my Oil shell parser into a standalone stdin/stdout filter, which is ready to be fuzzed:
https://github.com/oilshell/oil/blob/master/bin/osh_parse.py
https://github.com/oilshell/oil/issues/171
I'm already testing it by running it on more than a million lines of shell [1], which I imagine should provide a very good starting point for the AFL algorithm. I've only fuzzed one thing before but that's my understanding.
If anyone is itching to try out Python fuzzing, this might be a nice and realistic intro.
I made note of Fuzzbuzz on the bug.