using System;

public abstract class A<T>

{

public abstract T Prop { get; }

public abstract T this[int index] { get; set; }

public abstract event EventHandler Event;

public void Apply(T t1) { }

public abstract object ToObject(T t2);

public object Field;

public A() { }

public A(T t) { }

~A() { }

public static A<T> operator +(A<T> a1, A<T> a2) { return a1; }

}

public class A2 : A<string>

{

public override string Prop => "";

public override string this[int i]

{

get { return ""; }

set { }

}

public override event EventHandler Event

{

add { }

remove { }

}

public override object ToObject(string t) => t;

public void M()

{

A2 other = new();

other.Apply("");

}

}