Why is D unpopular?

[Ola Fosheim Grøstad]

On Monday, 8 November 2021 at 17:40:08 UTC, 12345swordy wrote:
> class as a reference type makes sense as you are dealing with 
> polymorphism.

Maybe so, but you could have the same typing scheme. Just make it 
a typing error to instantiate it as a non-reference type.

So you could for instance collapse struct/class, yet allow the 
programmer to specify that this particular struct/class can only 
be instantiated as heap-object.

And you could similarly put a ban on virtual members. So rather 
than having special cases struct and class, you allow the 
addition of constraints to a singular aggregate concept.