{"ast_node_type":"variable","tokens":[{"end":71,"kind":"keyword","start":0,"text":"let"}]}
                    let pos_in_file = start_bpos + BytePos(pos as u32);
                    // Count the number of chars since the start of the line by rescanning.
                    let line_begin_in_file = source_file.line_begin_pos(pos_in_file);