There are some auxiliary crates that are unused in the tests directory. I think it would be nice if compiletest could detect these and complain about them in some way.

This might be difficult due to ignored tests, or tests that are otherwise not run, which don't load enough information to know which auxiliary tests are used.

If it ends up being technically challenging, perhaps someone could just manually go through and clean up the orphans?
I've been intending to do that, but just haven't been able to make the time.

Example: https://github.com/rust-lang/rust/blob/master/tests/ui/auxiliary/default-ty-param-cross-crate-crate.rs