syntax_data: {"ast_node_type":"variable","tokens":[{"end":69,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let source_file_index = self.lookup_source_file_idx(sp.lo());
context_before:     pub fn is_imported(&self, sp: Span) -> bool {
context_after:         let source_file = &self.files()[source_file_index];