interfaces and contracts - new pattern

[Adam D. Ruppe]

On Tuesday, 3 December 2019 at 15:26:10 UTC, Ola Fosheim Grøstad 
wrote:
> Also the use of the term "covariant" here is confusing to me:

Yeah, to be honest, I forget what the terms mean, so I tend to 
avoid them. like my last email just talked about specialization 
and implicit casts which I think we all understand better anyway 
:)