{"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
        let extend_unit = |buf: &mut Vec<u8>, unit: MixedUnit| match unit {
        let mut has_error = None;
            MixedUnit::Char(c) => buf.extend(c.encode_utf8(&mut [0; 4]).as_bytes()),