There's no Rust codebase that takes hours to compile cold unless 1) you're compiling a massive codebase in release mode with LTO enabled, in which case, you've asked for it, 2) you've ported Doom to the type system, or 3) you're compiling on a netbook.

I'm curious if this is tracked or observed somewhere; crater runs are a huge source of information, metrics about the compilation time of crates would be quite interesting.