Declaration names sounds like a name of declaration -- something you
can use for analysis. It empathically isn't, and is just a label
displayed in various UI. It's important not to confuse the two, least
we accidentally mix semantics with UI (I believe, there's already a
case of this in the FamousDefs at least).
The proper fix I think is:
* move rust-lang/rust library crates to a separate workspace
* when packaging rust-src component, vendor sources of external deps
