syntax_data: {"ast_node_type":"variable","tokens":[{"end":71,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let file_idx = self.source_map.lookup_source_file_idx(pos);
context_before:         if !self.source_map.files().is_empty() {
context_after:             let file = &self.source_map.files()[file_idx];