{"ast_node_type":"variable","tokens":[{"end":79,"kind":"keyword","start":0,"text":"let"}]}
                    let filename = sm.filename_for_diagnostics(&loc.file.name);
                    buffer.puts(row_num - 1, 0, arrow, Style::LineNumber);
                    let offset = sm.doctest_offset_line(&loc.file.name, loc.line);