what was wrong with struct & class in C++?

[Christopher Wright]

Walter Bright wrote:
> Yigal Chripun wrote:
>> for me, the distinction between PODs and "objects" should be the 
>> polymorphic behavior, not the size of it (maybe i didn't explain 
>> myself properly). Am i completely wrong here?
> 
> You're right. Any object designed for inheritance or polymorphism should 
> properly be a reference type.

Is this because it is too difficult to implement polymorphism for value 
types safely and efficiently right now?

There's the slicing problem, of course, but there should be ways around 
that: worst case, you could rebuild the current stack frame each time 
you assign a polymorphic struct, but the effects on performance would be 
unpleasant. More happily, you could handle polymorphic structs like 
classes, but copy on (non-const) assignment.

That would be allowed in D, if you could overload T.opAssign(T).