{"ast_node_type":"variable","tokens":[{"end":28,"kind":"keyword","start":0,"text":"let"}]}
        let err_inner_expr =
        let err_pat = self.pat_tuple_struct(sp, err_path.clone(), thin_vec![binding_pat]);
            self.expr_call(sp, self.expr_path(err_path), thin_vec![binding_expr.clone()]);