pub fn resolve_external(db: &dyn Db, r: &ExternalRef) -> TyExpand description
The Phase-3 seam. Resolve a cross-file reference. In Phase 2 this is always
Ty::Unknown — a type that never warns, never cascades a diagnostic, and is elided from
hover. Funnel every “would need another file” path through here so Phase 3 has exactly one
function to reimplement.