You should note that "cargo clean" causes dependencies to be rebuilt next build as well; a regular "cargo build" would only re-compile your module and re-link with already-built dependencies, and so should be a fair bit faster.
Good point. I did that on purpose in order to do a full rebuild -- but I suppose for the purposes of "is rustc fast", it's actually more interesting to just do a build without clean (although one would have to manually remove the built binary and/or change the code in order to force a rebuild?).
And finally, a smaller project:
According to tokei (which is a blazingly fast cloc tool), there's ~100k cloc of rust in servo, ~7500 cloc of Rust in crates.io (but that doesn't include all the dependencies...).After doing a clean install of rust stable with multirust, the combined cloc of stuff under ~/.multirust...cargo/src and tokei is ~11.5k cloc of rust, along with ~ 1400 cloc of c++.