Rustc guarantees code that compile before continues to compile. In this case they modified the old hard error that you could opt out of into a deny by default

Rustc guarantees code that compile before continues to compile. In this case they modified the old hard error that you could opt out of into a deny by default lint. Additionally if you opt out of the lint you get progress notifications of how much work has been done. Looks like the whole thing is still statement based to avoid slow machines breaking on a timer.