Copy constructor of HashSet does not copy

[joelverhagen]

Repro:

using System.Diagnostics;

namespace Knapcode
{
    public static class ClassA
    {
        public static void MyMethod()
        {
            var a = new HashSet<int>();
            a.Add(1);
            a.Add(2);
            var b = new HashSet<int>(a);
            Console.WriteLine(b.Count);
        }

    }
}

Expected: 2, actual: 0