Function trait_ref_impl_id 

fn trait_ref_impl_id<'tcx>(
    tcx: TyCtxt<'tcx>,
    selcx: &mut SelectionContext<'_, 'tcx>,
    param_env: ParamEnv<'tcx>,
    trait_ref: TraitRef<'tcx>,
) -> Option<(DefId, GenericArgsRef<'tcx>)>