rust-lang
Clarify `use $crate` restriction
The previous wording for this restriction was pretty confusing to me. I don't remember what I was thinking when I wrote it, and I can't find any historical explanation either. use paths can use $crate as long as they have more than one segment (use $crate::foo is obviously OK).
I have rewritten this to make it clear it is specifically about use $crate. One could say that restriction is already covered by the previous point that says use crate; requires an as, but for some reason use $crate as foo doesn't work either. So I have left this as a separate rule for now.
cc https://github.com/rust-lang/rust/pull/146972#discussion_r2376951695 for context.
https://github.com/yaahc/rust/blob/adaa838976ff99a4f0661136322f64cb466b58a0/compiler/rustc_resolve/src/build_reduced_graph.rs#L630-L631 is the logic that controls this, it doesn't make a carveout for renaming imports but it doesn't mention them either so I'm not positive if that means it was intended to also disallow this case.
https://github.com/rust-lang/rust/pull/45846 is the PR where this logic was introduced. I did a quick search of the discussion on this PR and the associated PR, tracking issue, and RFC (discussion and content) and honestly couldn't find any mention of the $crate syntax at all outside of the PR diff itself. If I had to guess I'd assume this was probably an oversight. @petrochenkov's comment https://github.com/rust-lang/rust/issues/35612#issuecomment-578425321 seems to support this theory.
much better example: https://github.com/rust-lang/rust/pull/146972#discussion_r2382960171 in this one vadim explicitly mentions that renaming $crate should be allowed. Also looks like the contributor on this PR is quite actively working on improving the situation and consistency of this logic, I'll make sure any updates they make get properly integrated into the associated language in the reference.
