{"ast_node_type":"variable","tokens":[{"end":98,"kind":"keyword","start":0,"text":"let"}]}
                let return_def = self.create_def(return_id, None, DefKind::OpaqueTy, return_span);
                let (return_id, return_span) = coroutine_kind.return_id();
                self.with_parent(return_def, |this| this.visit_fn_ret_ty(output));