I think that listing behaviour could eventually be landed on rustc itself, but as it happens I am working on a listing tool, so I might just prototype it there

I think that listing behaviour could eventually be landed on rustc itself, but as it happens I am working on a listing tool, so I might just prototype it there first! The benefit of telling users "you can split this section off to its own crate" is that the "break" of that can't ever be silent.