pub fn suggest_arbitrary_trait_bound<'tcx>(
    tcx: TyCtxt<'tcx>,
    generics: &Generics<'_>,
    err: &mut DiagnosticBuilder<'_>,
    trait_pred: PolyTraitPredicate<'tcx>,
    associated_ty: Option<(&'static str, Ty<'tcx>)>
) -> bool