851a03492e
3690: ra_hir: add more docs r=matklad a=Veetaha Cited from [hear](https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Fwg-rls-2.2E0/topic/hover/near/191446937) Co-authored-by: veetaha <veetaha2@gmail.com>