syntax_data: {"ast_node_type":"other","tokens":[{"end":69,"kind":"keyword","start":0,"text":"(Some((fn_def_id,"}]}
source_snippet:             (Some((fn_def_id, fn_args)), RtnMode::ForDiagnostic) => {
context_before:         match (fn_args, RTN_MODE.with(|c| c.get())) {
context_after:                 self.pretty_print_opaque_impl_type(def_id, args)?;