Adding a new design constraint to D

[Mike Parker]

On Tuesday, 14 June 2022 at 12:28:24 UTC, Ola Fosheim Grøstad 
wrote:
> On Tuesday, 14 June 2022 at 12:19:40 UTC, Mike Parker wrote:\
>> And Paul did show you how to do that with `child.Foo._c`.
>
> Which is a pointless thing to say, you are still violating the 
> subtyping relationship.

So then what do you do when your direct access to `child._c` 
suddenly starts causing a subtle bug because someone added later 
added a `_c` member to the public interface of `Bar`? Private 
members are not inherited and do not impact the public interface.