Comment by tedunangst
1 day ago
I just ran cargo check on nushell, and it took a minute and a half. I didn't time how long it took to compile, maybe five minutes earlier today? So I would call it faster, but still not fast.
I was all excited to conduct the "cargo check; mrustc; cc" is 100x faster experiment, but I think at best, the multiple is going to be pretty small.
Did you do it from a clean build? In that case, it's actually a slightly misleading metric, since rust needs to actually compile macros in order to typecheck code that uses them. (And therefore must also compile all the code that the macro depends on.) My bad for suggesting it, haha. Incremental cargo check is often a better way of seeing how long typechecking takes, since usually you haven't modified any macros that will need to be recompiled. On my project at work, incremental cargo check takes `1.71s`.
Side note: There's an effort to cache proc macro invocations so that they get executed only once if the item they annotate hasn't changed: https://github.com/rust-lang/rust/pull/129102
There are multiple caveats on providing this to users (we can't assume that macro invocations are idempotent, so the new behavior would have to be opt in, and this only benefits incremental compilation), but it's in our radar.
A ton of that is actually still doing codegen (for the proc macros for example).