{"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
        let trait_def_id = tcx.parent(fn_def_id);
        debug!("RPITIT fn_def_id={fn_def_id:?} opaque_def_id={opaque_def_id:?}");
        let opaque_ty_generics = tcx.generics_of(opaque_def_id);