Reimplementing the bulk of std.meta iteratively

[Stefan Koch]

On Wednesday, 30 September 2020 at 23:17:27 UTC, Timon Gehr wrote:
> On 29.09.20 01:37, Stefan Koch wrote:
>> On Monday, 28 September 2020 at 21:27:56 UTC, Timon Gehr wrote:
>>> On 28.09.20 23:08, claptrap wrote:
>>>> Instead of first class types
>>>
>>> (Stefan's type functions do not give you first-class types. A 
>>> first-class type you could put in a runtime variable.)
>> 
>> That's true. At least as it stands right now.
>> I _could_ give  the alias a physical form at runtime.
>> (By doing the same thing that the reify template does (or 
>> rather will eventually do), that is exporting _all_ the 
>> properties of the type into an object)
>> 
>> However I am not actually sure what the use of this would be.
>> All usage that I have seen, is in generating code, which is 
>> kindof useless if it does not happen at compile time.
>> 
>> Perhaps there are others?
>
> It's not a first-class type if you can't declare a variable of 
> that type. If this does not work, it's not first-class, it's 
> syntax sugar for reification:
>
> type t = int;
> auto f = (t x)=>x;

Yes I do understand that.
I was wondering about practical usecases.
As far as I an aware, if I made the leap to first class types, 
that would make all usage of them into static polymorphism. 
(equivalent to templates)
And with that all the issues come back.