No we should not support enum types derived from strings

[Andrei Alexandrescu]

On 5/9/21 8:57 PM, deadalnix wrote:
> On Friday, 7 May 2021 at 16:43:20 UTC, Andrei Alexandrescu wrote:
>> Well you see here is the problem. An enum with base string can be 
>> coerced to a string, but is not a true subtype of string. This came to 
>> a head with ranges, too - you can pop off the head of a string still 
>> have a string, but if you pop off the head of an enum string you get 
>> some enum value that is not present in the set of enum values. 
>> Concatenation has similar problems, e.g. s ~ s for enum strings yields 
>> string, not an enum string. (Weirdly s ~= s works...)
>>
> 
> Popping the head out of an enum value ought to be a string, not that 
> enum's value. I don't really see where the problem is here, this is 
> subtyping 101.

So you have a range r of type T.

You call r.popFront().

Obvioulsly the type of r should stay the same because in D variables 
don't change type.

So... what gives, young Padawan?

No, this is not subtyping 101.