{"ast_node_type":"variable","tokens":[{"end":25,"kind":"keyword","start":0,"text":"let"}]}
        let mut visitor =
    ) -> (FxIndexSet<(ty::Region<'tcx>, usize)>, FxIndexSet<(Ty<'tcx>, usize)>) {
            GATArgsCollector { gat, regions: FxIndexSet::default(), types: FxIndexSet::default() };