Function deeply_normalize 

pub fn deeply_normalize<'tcx, T, E>(
    at: At<'_, 'tcx>,
    value: Unnormalized<'tcx, T>,
) -> Result<T, Vec<E>>
where
    T: TypeFoldable<TyCtxt<'tcx>>,
    E: FromSolverError<'tcx, NextSolverError<'tcx>>,

Deeply normalize all aliases in value. This does not handle inference and expects its input to be already fully resolved.