public class SomeEqualityComparer : IEqualityComparer<string>
    {
        public bool Equals(string x, string y)
        {
            return true;
        }

        public int GetHashCode(string obj)
        {
            if (obj == null)
            {
                // This raises CA1065!
                throw new ArgumentNullException(nameof(obj));
            }

            return 0;
        }
    }