Why are structs and classes so different?

[Guillaume Piolat]

On Sunday, 15 May 2022 at 15:26:40 UTC, Kevin Bailey wrote:
> I'm trying to understand why it is this way. I assume that 
> there's some benefit for designing it this way. I'm hoping that 
> it's not simply accidental, historical or easier for the 
> compiler writer.

Perhaps someone more informed will chime in, but there is a 
reason to avoid object inheritance with value types, and force 
them to be reference types.

https://stackoverflow.com/questions/274626/what-is-object-slicing

If we want to avoid that problem, then object with inheritance 
and virtual functions have to be reference types.

But you still need values types. So now you have both struct and 
class, like in C# (Hejlsberg, 2000).

For an escape hatch, D has library ways to have structs with 
virtual functions (there is a DUB package for that), and classes 
on the stack (Scoped!T, RefCounted!T, a __traits).