966d5b0e34
The lint is very slow as it doesn't cache the deeply nested check for the attribute. If we cache it, we can reduce the time spent on checking `rustc_borrowck` from 28s to 9s, which is a nice improvement. In the profile, the time inside `has_sig_drop_attr` goes from 66% to 0.2%, which is a lot more reasonable. See the PR for nice graphs.