What are the prominent downsides of the D programming language?

[Abdulhaq]

On Wednesday, 30 September 2020 at 08:44:26 UTC, Mike Parker 
wrote:
> On Wednesday, 30 September 2020 at 00:57:52 UTC, Jean-Louis 
> Leroy wrote:
>
> I read a game development book[1] years ago where the author 
> was pushing this approach quite strongly, saying he had 
> published several games where it was used. He referred to it as 
> "mixin inheritance". As long as you reserve MI for introducing 
> behaviors into classes and constrain derived "is-a" 
> relationships to a single (preferably shallow) line in the 
> hierarchy, you are less likely to run into problems.
>
> [1] 
> https://www.amazon.com/Object-Oriented-Game-Development-Julian-Gold/dp/032117660X

Yes this is a well known pattern usually called a mixin class:

https://en.wikipedia.org/wiki/Mixin

It's a valid use case, but can easily be achieved in other ways.