{"ast_node_type":"other","tokens":[{"end":73,"kind":"keyword","start":0,"text":"Ok(infer_ok)"}]}
            Ok(infer_ok) => self.register_infer_ok_obligations(infer_ok),
        ) {
            Err(_) => self.sig_of_closure_no_expectation(expr_def_id, decl, closure_kind),