using System;

public class Program

{

    public static void Foo(object o)

    {

        if(!(o is string s))

        {

            return;

        }

        Console.WriteLine(s);   // <-- OK

    }

    public static void Bar(object o)

    {

        if((o is string s) == false)

        {

            return;

        }

        Console.WriteLine(s); // <-- Use of unassigned local variable 's'

    }

    public static void Main()

    {

    }

}