{"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
        let self_arg = &mut inputs_and_output[0];
        let mut inputs_and_output = sig.inputs_and_output.to_vec();
        debug_assert!(tcx.generics_of(def_id).has_self && *self_arg == tcx.types.self_param);