Why can't a class extend its own nested class in C#?

Question

For example:

public class A : A.B
{
    public class B { }
}

Which generates this error from the compiler:

Circular

Answer 1

Regarding questions about what I was attempting to do:

Basically, I wanted to create a class that had a composition relationship with itself, but I didn't want to have the contained object to contain other objects and therefore create a chain with many "A has-a A has-a A has-a A has-a..." relationships. So my thought at the time was do something like this:

public class A : A.AA
{
    public class AA
    {
        // All of the class's logic
    }

    private AA _containedObject;
}

Which at the time seemed pretty slick but in retrospect I'm not so sure...

I had rummaged through Google and didn't find any good discussion on it so I thought I'd post it here.

However, within the comments of a post at Eric Lippert's Blog he gives examples of a class implementing a nested interface as well as a class implementing a generic interface with a nested class as the type argument (which doesn't compile and he calls a "bug" in the current compiler). Both of those examples concern interfaces so I was wondering if there was some special rules with nested classes. And it seems there are.