{"ast_node_type":"variable","tokens":[{"end":81,"kind":"keyword","start":0,"text":"let"}]}
        let prev_ret_ty = mem::replace(&mut self.return_ty, body_ret_ty.clone());
        let prev_closure = mem::replace(&mut self.current_closure, id);
        let prev_ret_coercion = self.return_coercion.replace(CoerceMany::new(body_ret_ty));