title: Partial classes in different namespace are not being recognized correctly
body: <p>I have a partial class that is split over two namespaces. The problem is that if I have an interface implemented on one of the partials, it is not recognized on the counterpart partial class. For example, I would expect the below to return true for being recognized as <code>ILastModified</code> (C# fiddle at <a href="http://ideone.com/heLDn0" rel="nofollow noreferrer">http://ideone.com/heLDn0</a>):</p>
  <pre><code>using System;
  using MyNamespace.One;
   
  public class Test
  {
      public static void Main()
      {
          var item = new Product();
          Console.WriteLine(item is ILastModified); //RETURNS FALSE??!
      }
  }
   
  interface ILastModified
  {
      DateTime LastModified { get; set; }
  }
   
  namespace MyNamespace.One
  {
      public partial class Product
      {
          public int ID { get; set; }
      }
  }
   
  namespace MyNamespace.Two
  {
      public partial class Product : ILastModified
      {
          public DateTime LastModified { get; set; }
      }
  }
  </code></pre>