syntax_data: {"ast_node_type":"other","tokens":[{"end":59,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // be empty, so the working directory will be used.
context_before:         // but this is okay because the directory determined by `path.pop()` will
context_after:         let (filename, _) = self.path_mapping.map_filename_prefix(&filename);