using System;

using System.Threading.Tasks;

​

public class Program

{

    public class Base

    {

    }

​

    public class Derived : Base

    {

    }

​

    public static void Main()

    {

        Func<Task<Base>> d = GetBase;

        Func<Task<Derived>> e = d;

        Task<Base> dd = GetDerived();

        Console.WriteLine("Hello World");

    }

​

    public static Task<Base> GetBase()

    {

        return Task.FromResult(new Base());

    }

​

    public static Task<Derived> GetDerived()

    {

        return Task.FromResult(new Derived());

    }

}