{"ast_node_type":"variable","tokens":[{"end":93,"kind":"keyword","start":0,"text":"let"}]}
                    let underline_end = (span_start_pos + start + sub_len) as isize + offset;
                    let underline_start = (span_start_pos + start) as isize + offset;
                    assert!(underline_start >= 0 && underline_end >= 0);