/// <inheritdoc/>
        protected override Provider VisitDistinct(DistinctProvider provider)
        {
            OnRecursionEntrance(provider);
            var source = VisitCompilable(provider.Source);

            OnRecursionExit(provider);
            if (source == provider.Source)
            {
                return(provider);
            }
            return(new DistinctProvider(source));
        }
 /// <summary>
 /// Visits <see cref="DistinctProvider"/>.
 /// </summary>
 /// <param name="provider">Distinct provider.</param>
 protected abstract Provider VisitDistinct(DistinctProvider provider);