class template conflict

[Basile B.]

On Sunday, 23 December 2018 at 12:09:31 UTC, Michelle Long wrote:
> class X
> {
>
> }
>
> class X(int N) : X
> {
>
> }
>
> Is there any real reason we can't do this?
>
> It is very nice to be able to treat X like the base and X!n as 
> a derived class.
>
> Sure we can do
>
> class X(int N) : X!0
> {
>    static if(N == 0)
>    {
>    }
> }
>
> but this is very ugly, in my code I always have to use X!0 as 
> the basis!
>
> I do not think there is any harm to allow this since the 
> templated class always has to specify N. It is not like we can 
> do
>
> class X(int N = 0) : X
> {
>    static if(N == 0)
>    {
>    }
> }
>
>
> Actually we can, so... I don't see the point in not allowing 
> the first case, they are logically equivalent. That static if 
> is just ugly and it is defining the base class inside the 
> derived class which seems unnatural.

You have this option too:

```
template X(N...)
if (N.length == 0 ||
     N.length == 1 && is(typeof(N[0]) == int))
{
     static if (N.length == 0)
     class X {}

     else class X : X!() {}
}

auto base = new X!();
auto derived = new X!8;
```

More simple is : do not use the same identifier ;)