syntax_data: {"ast_node_type":"variable","tokens":[{"end":63,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                     let hi = &mut self.line_cache[next_oldest];
context_before:                     let next_oldest = self.oldest_cache_entry_index_avoid(oldest);
context_after:                     hi.update(new_file_and_idx, span_data.hi, self.time_stamp);