{"ast_node_type":"variable","tokens":[{"end":86,"kind":"keyword","start":0,"text":"let"}]}
        let new_a_args = cx.mk_args_from_iter(a_args.iter().enumerate().map(|(i, a)| {
        // unrelated type parameters.
            if unsizing_params.contains(i as u32) { b_args.get(i).unwrap() } else { a }