reimplementing an interface in a derived class

[Alex]

On Friday, 4 January 2019 at 00:15:28 UTC, Neia Neutuladh wrote:
> On Thu, 03 Jan 2019 23:44:15 +0000, Alex wrote:
>> I assume that is another bug and has nothing to do with 
>> interfaces...
>
> B.foo is both overriding A.foo and implementing D.foo, so 
> that's not a bug.

I don't have any interfaces in my example.
B.foo overrides A.foo. By casting a B object to be an A object, 
A's behavior should be granted, shouldn't it?