Inheritance of mixin

[tsbockman via Digitalmars-d]

On Saturday, 30 April 2016 at 01:06:18 UTC, Andrew Benton wrote:
> Additionally, any libraries that provide a base class with a 
> mixin require inheritors to know about that mixin and provide 
> it in their own code.  It certainly isn't going to happen in 
> every case, but if the needed functionality is provided by 
> mixins, then users of the library could have problems.

I spent a while trying to figure out how to automatically verify 
that a mixin required by a class hierarchy is included in all 
derived classes, and failed to come up with a general purpose 
solution. (I found a partial solution involving a `this T` 
templatized constructor, but it had a lot of problems.) So, I 
agree now that this is a problem worth solving.

It could be fixed by extending template mixins as you and others 
have proposed.

Another possible solution would be to fix `this T` template 
functions to be virtual, and automatically generate an override 
for each derived class. This would directly solve the most common 
use case, and also provide an (awkward) way to automatically 
verify mixin inclusion in derived classes for more complex 
scenarios.