{"ast_node_type":"other","tokens":[{"end":22,"kind":"keyword","start":0,"text":"Ok(MatrixRow"}]}
        Ok(MatrixRow {
    ) -> Result<MatrixRow<'p, Cx>, Cx::Error> {
            pats: self.pats.pop_head_constructor(cx, ctor, ctor_arity, ctor_is_relevant)?,