{"ast_node_type":"variable","tokens":[{"end":63,"kind":"keyword","start":0,"text":"let"}]}
        let tt::TokenTree::Subtree(subtree) = &self.0[0] else {
    pub(crate) fn top_subtree(&self) -> &tt::Subtree<S> {
            unreachable!("the first token tree is always the top subtree");