syntax_data: {"ast_node_type":"variable","tokens":[{"end":54,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let chpos = self.bytepos_to_file_charpos(pos);
context_before:     fn lookup_file_pos(&self, pos: RelativeBytePos) -> (usize, CharPos) {
context_after:         match self.lookup_line(pos) {