Covariance, delegates and generic type constraints [duplicate]

Question

public void Foo<T>(Func<T> bar)
 where T: IMyInterface
{
   Func<IMyInterface> func = bar;
}

It has been a while since I'd understood covariance, but shouldn't this compile?

Anything bar can return is also an IMyInterface. What seems to be the problem?

Answer 1

Is this a covariance bug in C# 4?

the correct code is:

public void Foo<T>(Func<T> bar)
 where T: class, IMyInterface
{
   Func<IMyInterface> func = bar;
}