Registering concrete types that implement common interfaces with Autofac

Consider the following structure as a registration object with Autofac 3.0.0:

class Something
{
    public int Result { get; set; }
}

class SomethingGood : Something
{
    private int _good;
    public int GoodResult {
        get { return _good + Result; }
        set { _good = value; }
    }
}

interface IDo<in T> where T : Something
{
    int Calculate( T input );
}

class MakeSomethingGood : IDo<SomethingGood>
{
    public int Calculate( SomethingGood input ) {
        return input.GoodResult;
    }
}

class ControlSomething
{
    private readonly IDo<Something> _doer;
    public ControlSomething( IDo<Something> doer ) {
        _doer = doer;
    }

    public void Show() {
        Console.WriteLine( _doer.Calculate( new Something { Result = 5 } ) );
    }
}

      

        
        
        
      

    

I'm trying to register a specific type of MakeSomethingGood and then resolve it using a contravariant interface.

var builder = new ContainerBuilder();
builder.Register( c => new MakeSomethingGood() ).As<IDo<SomethingGood>>();
builder.Register( c => new ControlSomething( c.Resolve<IDo<Something>>() ) ).AsSelf();

var container = builder.Build();
var controller = container.Resolve<ControlSomething>();

      

        
        
        
      

    

... and Resolve

fails because no components were found forIDo<Something>

What am I doing wrong?

thank