The worst offenders vary a lot by particular codebase. I had a crate where the compile times were bad due to trait bounds. I was able to refactor to drop times

The worst offenders vary a lot by particular codebase. I had a crate where the compile times were bad due to trait bounds. I was able to refactor to drop times from ~2 minutes to ~6seconds! That should'nt have been necessary for me to refactor though. Sometimes its llvm, sometimes its rust macros encouraging HUGE functions which then leads to slow llvm optimizations. Sometimes it's large use of generics. Sometimes it is the linker. There are various ways to hit slow compile times.