{"ast_node_type":"variable","tokens":[{"end":79,"kind":"keyword","start":0,"text":"let"}]}
        let final_tupled_upvars_type = Ty::new_tup(self.tcx, &final_upvar_tys);
        // and unify the upvar tuple type in the closure with it:
        self.demand_suptype(span, args.tupled_upvars_ty(), final_tupled_upvars_type);