{"ast_node_type":"function","tokens":[{"end":93,"kind":"keyword","start":0,"text":"fn"}]}
    fn unescape(s: &str, mut callback: impl FnMut(Range<usize>, Result<char, EscapeError>)) {
    // char/byte is not used. For simplicity, we return an arbitrary placeholder char.
        unescape_c_str(s, |range, _res| callback(range, Ok('_')))