using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

    }

​

    public abstract class Foo

    {

        public abstract T Poo<T>(T param)

            where T : Person;

    }

​

    public class Bar : Foo

    {

        public override Person Poo(Person param)

        {

            return null;

        }

    }

​

    public class Person

    {

        public int Age

        {

            get;

            set;

        }

    }

}