syntax_data: {"ast_node_type":"other","tokens":[{"end":93,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // Return early if the file containing beginning of span doesn't contain end of span.
context_before:         // If the entry doesn't point to the correct file, get the new file and index.
context_after:         let new_file_and_idx = if !file_contains(&self.line_cache[oldest].file, span_data.lo) {