syntax_data: {"ast_node_type":"function","tokens":[{"end":72,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
context_before:     #[instrument(skip(self), level = "debug")]
context_after:         match r.kind() {