Big Bummer

Ian Griffiths asks a great question in the comments on my post about System.Xml 2.0. Here it is:

That's excellent! But I have one question: why can't I do this?:

Book book = reader.ReadAsObject < Book > ();

What's with all this casting, in a world with generics? (Of course what you really want is for the template parameter to be inferred, but sadly you cannot infer template arguments from function return types.)

A quick experiment verified my assumption: generics are not CLS Compliant, as evidenced by this code:

using System;
[assembly:CLSCompliant(true)]

namespace GenericsCLSCompliant
{
  public class App
  {
    static void Main(string[] args)
    {
      new Class1<App>().DoSomething(new App());
    }
  }

  public class Class1<T> where T : new()
  {
    public void DoSomething(T t)
    {
    }
  }
}

and the ensuing compiler error:

error CS3024: 'GenericsCLSCompliant.Class1<T>': type parameters are not CLS-compliant

What this means is that the important bits of the CLR libraries cannot leverage generics. This is a crying shame.