I mean … trees, what you’re describing is a challenging situation. But also, you don’t have to take that all on at once all the time. You ought to have corners of your code where you have guarantees and invariants you can trust that make your life easier. At least I would hope.

Also you made a general statement about writing correct code being insanely hard. I mean, writing hard code is hard, but many if not most of the things we do in this profession are not in that category. And most of the correctness we need to achieve isn’t insanely hard. Agreed that there are of course areas where the confluence of challenges can be extremely challenging.