Function evaluate_host_effect_from_conditionally_const_item_bounds 

fn evaluate_host_effect_from_conditionally_const_item_bounds<'tcx>(
    selcx: &mut SelectionContext<'_, 'tcx>,
    obligation: &HostEffectObligation<'tcx>,
) -> Result<ThinVec<PredicateObligation<'tcx>>, EvaluationFailure>

Assembles constness bounds from ~const item bounds on alias types, which only hold if the ~const where bounds also hold and the parent trait is ~const.