syntax_data: {"ast_node_type":"function","tokens":[{"end":91,"kind":"keyword","start":0,"text":"pub"}]}
source_snippet:     pub fn lookup_line(&self, pos: BytePos) -> Result<SourceFileAndLine, Arc<SourceFile>> {
context_before:     /// If the corresponding `SourceFile` is empty, does not return a line number.
context_after:         let f = self.lookup_source_file(pos);