As the grammar gets large, compile times grow a lot. A grammar similar to C but still a lot simpler takes about 2 or 3 minutes to compile and it gets recompiled on any change to the project. I had to put it in a separate crate to avoid it. Expressions with many precedence levels seem to be the main cause but even without them it takes way too long.

Not sure if related but doc tests also seem to take ages when using plex and a large grammar.