I usually do Illoai top lane, and I've gotten pretty good at winning against most matchups I run into, or at least finding ways to stalemate the lane and go even.
I recently had a game against a Rengar top for the first time and got demolished. I'm not trying to call it OP, I've lost plenty of lanes in first time matchups while I try to figure out how to handle that champion. I just this time did not really come up with a plan for what I could have done to make it better. It seems like he can cross the entire lane from the top bushes, so just standing far from them doesn't seem viable. Staying under my tower for the first 6 levels would probably work alright, but if Rengar decides to just not push that seems like begging to never get any CS in all game.
So how does one go about laning against Rengar in the top lane?