No we should not support enum types derived from strings

[Ola Fosheim Grøstad]

On Tuesday, 11 May 2021 at 21:36:46 UTC, Andrei Alexandrescu 
wrote:
> There's no true subtyping or polymorphism with value semantics.

I think you guys need to agree on what you mean by "type" and 
"subtype".

Mathematically a type would be a set of states and a set of 
operators that can take you between the states.  A subtype is 
just a reduced set of states/operators where operators keep you 
within the set of states.

In OO a type is an abstraction (reduced set) of the states that 
the entity you model in The Real World has. A subclass in OO is 
increasing the number of states/operators, but decreasing the 
number of Real World entities covered.

So these twi notions of "subtype" are opposite.

> primitives across said range of types. With enums that's 
> onerous; as soon as you "derive" an enum from int you figure 
> that ++x can't reasonably be implemented. Same goes for enum

In C enums are subtypes of int. You reduce the number of states.

C enums are not sound, because operators can take you out of the 
allowed set of states in a heartbeat.

Anyway, I've given up following this discussion.

Just define the desirable outcome (practical design) and forget 
about the theoretical aspects... then others might be able to 
understand where the viewpoints differ.