using System;

using Fluid;

​

public class Program

{

    class A

    {

        public bool Bar;

    }

​

    class B

    {

        public A a;

        public bool HasA => a is not { Bar: false };

    }

​

    public static void Main()

    {

        var a1 = new B { a = new A { Bar = true } };

        Console.WriteLine(a1.HasA);

​

        var a2 = new B { a = new A { Bar = false } };

        Console.WriteLine(a2.HasA);

​

        var a3 = new B { a = null };

        Console.WriteLine(a3.HasA);

    }

}