{"ast_node_type":"variable","tokens":[{"end":45,"kind":"keyword","start":0,"text":"let"}]}
        let (param_tys, ret_ty) = match res {
            derefed_callee.callable_sig(self.db).is_some_and(|sig| sig.is_varargs) || res.is_none();
            Some((func, params, ret_ty)) => {