{"ast_node_type":"variable","tokens":[{"end":73,"kind":"keyword","start":0,"text":"let"}]}
            let tt::TokenTree::Subtree(subtree) = &tt[subtree_idx] else {
        'pop_finished_subtrees: while let Some(&subtree_idx) = subtrees_stack.last() {
                unreachable!("non-subtree on subtrees stack");