using System;

class Program
{
    static void Main()
    {
        using (IDisposable x = null, y = null)
            Console.WriteLine(x);
    }
}

using System;

class Program
{
    static void Main()
    {
        IDisposable y;
        using (y = null)
            Console.WriteLine(x); // error CS0103: The name 'x' does not exist in the current context
    }
}