{"ast_node_type":"variable","tokens":[{"end":58,"kind":"keyword","start":0,"text":"let"}]}
    let v_candidates = v.ancestors().skip(v_depth - keep);
    let u_candidates = u.ancestors().skip(u_depth - keep);
    let (res, _) = u_candidates.zip(v_candidates).find(|(x, y)| x == y)?;