Container.cs

using System.Collections.Generic;
using System.Collections.Immutable;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using System.Linq;

namespace OmniSharp.Extensions.DebugAdapter.Protocol.Models
{
    public static class Container
    {
        [return: NotNullIfNotNull("items")]
        public static Container<T>? From<T>(IEnumerable<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From<T>(params T[] items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From<T>(List<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From<T>(in ImmutableArray<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From<T>(ImmutableList<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };
    }

    public class Container<T> : ContainerBase<T>
    {
        public Container() : this(Enumerable.Empty<T>())
        {
        }

        public Container(IEnumerable<T> items) : base(items)
        {
        }

        public Container(params T[] items) : base(items)
        {
        }

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From(IEnumerable<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static implicit operator Container<T>?(T[] items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From(params T[] items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static implicit operator Container<T>?(Collection<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From(Collection<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static implicit operator Container<T>?(List<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From(List<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static implicit operator Container<T>?(in ImmutableArray<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From(in ImmutableArray<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static implicit operator Container<T>?(ImmutableList<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };

        [return: NotNullIfNotNull("items")]
        public static Container<T>? From(ImmutableList<T>? items) => items switch {
            not null => new Container<T>(items),
            _        => null
        };
    }
}