Implementing interfaces using alias this

[Balagopal Komarath via Digitalmars-d-learn]

On Wednesday, 14 June 2017 at 11:40:02 UTC, ketmar wrote:
> interfaces *require* a full-featured class, with VMT, and some 
> hidden pointers to support hidden interface machinery.

I don't think that is the problem here. The type Test!Duck is a 
class and that type is the one implementing the interface.