fn confirm_param_env_candidate<'cx, 'tcx>(
    selcx: &mut SelectionContext<'cx, 'tcx>,
    obligation: &Obligation<'tcx, AliasTy<'tcx>>,
    poly_cache_entry: PolyProjectionPredicate<'tcx>,
    potentially_unnormalized_candidate: bool
) -> Progress<'tcx>