syntax_data: {"ast_node_type":"variable","tokens":[{"end":82,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                     let next_oldest = self.oldest_cache_entry_index_avoid(oldest);
context_before:                     let new_file_and_idx = Some((Arc::clone(&lo.file), lo.file_index));
context_after:                     let hi = &mut self.line_cache[next_oldest];