What are the prominent downsides of the D programming language?

[Paulo Pinto]

On Monday, 21 September 2020 at 09:35:10 UTC, Ruby The Roobster 
wrote:
> On Monday, 21 September 2020 at 09:29:21 UTC, Tomcruisesmart 
> wrote:
>> Hi,
>> I'm looking for healthy conversation.
>> What are the prominent downsides of the D programming language?
>
> One downside is that classes can't inherit from multiple 
> classes.
>  I know that there is a thing called an interface which a class 
> can inherit more that one of those. Thing is, functions in 
> interfaces have to be abstract.  Also, member variables 
> declared in an interface have to be static, and the only member 
> functions that are defined have to be static. Why can't we just 
> inherit from multiple classes?

This is known as Protocol oriented programming and goes back to 
Objective-C protocols, CLU and Standard ML modules.

It is also the basis of ECS heavily used alongside data oriented 
programming in all major game engines.

Ah, and COM/UWP, which have been the main way Windows APIs are 
made available since Vista, building on top of Longhorn's OOP ABI 
ideas.

Maybe there is a learning path there.