using System.Collections.Generic;

using System;

public class Program {

    public static void Main() {

        var context1 = new ListAndSetContext();

        Console.WriteLine($"ListAndSetContext.list() returns {declTypeName(context1.list())}");

        Console.WriteLine($"ListAndSetContext.set() returns {declTypeName(context1.@set())}");

        Console.WriteLine();

        var context2 = new ReadOnlyListAndSetContext();

        Console.WriteLine($"ReadOnlyListAndSetContext.list() returns {declTypeName(context2.list())}");

        Console.WriteLine($"ReadOnlyListAndSetContext.set() returns {declTypeName(context2.@set())}");

        Console.WriteLine();

​

        var context3 = new ListAndReadOnlySetContext();

        Console.WriteLine($"ListAndReadOnlySetContext.list() returns {declTypeName(context3.list())}");

        Console.WriteLine($"ListAndReadOnlySetContext.set() returns {declTypeName(context3.@set())}");

        Console.WriteLine();

        var context4 = new ReadOnlyListAndReadOnlySetContext();

        Console.WriteLine($"ReadOnlyListAndReadOnlySetContext.list() returns {declTypeName(context4.list())}");

        Console.WriteLine($"ReadOnlyListAndReadOnlySetContext.set() returns {declTypeName(context4.@set())}");

        Console.WriteLine();

    }

    private static string declTypeName<T>(T expr) => typeof(T).Name;

    private class ListAndSetContext : Context<Config, List<int>, HashSet<string>> {

        public ListAndSetContext() : base(new Config()) {}

    }

    private class ReadOnlyListAndSetContext : Context<Config, IReadOnlyList<int>, HashSet<string>> {

        public ReadOnlyListAndSetContext() : base(new Config()) {}

    }

    private class ListAndReadOnlySetContext : Context<Config, List<int>, IReadOnlySet<string>> {

        public ListAndReadOnlySetContext() : base(new Config()) {}

    }

    private class ReadOnlyListAndReadOnlySetContext : Context<Config, IReadOnlyList<int>, IReadOnlySet<string>> {

        public ReadOnlyListAndReadOnlySetContext() : base(new Config()) {}

    }

}

​

public interface IConfig<out T0, out T1> where T0 : IReadOnlyList<int> where T1 : IReadOnlySet<string> {

    public T0 list();

    public T1 @set();

}

​

public class Config : IConfig<List<int>, HashSet<string>> {

    public List<int> list() => new List<int>(new []{ 1, 2, 3 });

    public HashSet<string> @set() => new HashSet<string>(new []{ "a", "b", "c" });

}

​

public interface IContext<T0, T1> where T0 : IReadOnlyList<int> where T1 : IReadOnlySet<string> {

    public T0 list();

    public T1 @set();

}

​

public class Context<C, T0, T1> : IContext<T0, T1> where C : IConfig<T0, T1> where T0 : IReadOnlyList<int> where T1 : IReadOnlySet<string> {

    private readonly C _config;

    public Context(C config) => this._config = config;

    public T0 list() => _config.list();

    public T1 @set() => _config.@set();

}