namespace System.Collections.Immutable
{
    [CollectionBuilder(typeof(ImmutableSortedSet), "Create")]
    [DefaultMember("Item")]
    public sealed class ImmutableSortedSet<T> : ICollection<T>, IEnumerable, IEnumerable<T>, IList<T>, IReadOnlyCollection<T>, IReadOnlyList<T>, IReadOnlySet<T>, ISet<T>, ICollection, IList, IImmutableSet<T>
    {
        [DefaultMember("Item")]
        public sealed class Builder : ICollection<T>, IEnumerable, IEnumerable<T>, IReadOnlyCollection<T>, ISet<T>, ICollection
        {
            public IComparer<T>! KeyComparer { get; set; }
        }
    }
}