fn is_type_structurally_recursive<'tcx>( tcx: TyCtxt<'tcx>, seen: &mut Vec<Ty<'tcx>>, shadow_seen: &mut Vec<AdtDef<'tcx>>, representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>, ty: Ty<'tcx>, sp: Span, field_id: Option<HirId>, force_result: &mut bool) -> Representability