{"ast_node_type":"variable","tokens":[{"end":64,"kind":"keyword","start":0,"text":"let"}]}
    let reachable_blocks = traversal::reachable_as_bitset(body);
        ReplacementFinder { targets, can_perform_opt, allowed_replacements: FxHashSet::default() };
    for (bb, bbdata) in body.basic_blocks.iter_enumerated() {