My comment is in response to "super cool idea, but I don't think it's going to help Rust compile speeds". Even a compiler that emits garbage IR from the fronten

My comment is in response to "super cool idea, but I don't think it's going to help Rust compile speeds". Even a compiler that emits garbage IR from the frontend would get 20x faster with a magic instant backend if 95% of time is currently spent in the backend. A magic instant backend is unrealistic, so Rust will need to move some of the current backend work to frontend work for things that can be done more efficiently on the frontend. But the fact remains that there is an opportunity for big improvement from a much faster backend.