{"ast_node_type":"other","tokens":[{"end":41,"kind":"keyword","start":0,"text":"reachable_vids:"}]}
    reachable_vids: FxHashSet<ty::TyVid>,
struct AnnotateUnitFallbackVisitor<'a, 'tcx> {
    fcx: &'a FnCtxt<'a, 'tcx>,