syntax_data: {"ast_node_type":"variable","tokens":[{"end":44,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let col = chpos - linechpos;
context_before:                 let linechpos = self.bytepos_to_file_charpos(linebpos);
context_after:                 debug!("byte pos {:?} is on the line at byte pos {:?}", pos, linebpos);