{"ast_node_type":"other","tokens":[{"end":53,"kind":"keyword","start":0,"text":"Ok(snippet)"}]}
        Ok(snippet) if snippet.ends_with("self") => {
    match tcx.sess.source_map().span_to_snippet(span) {
            (span.with_hi(span.hi() - BytePos(4)).shrink_to_hi(), "mut ".to_string())