On type functions

[Stefan Koch]

On Sunday, 3 May 2020 at 11:05:13 UTC, Panke wrote:
> On Sunday, 3 May 2020 at 10:52:37 UTC, Stefan Koch wrote:
>>
>> If there are any other open questions about how this is 
>> supposed to work I am happy to answer them.
>
> I think type functions are important work.
>
> What operations are available on types? Can I do something like 
> this:
>
> ---
> TStruct structFromSpec(string spec)
> {
>     TStruct result;
>     for (field; parseFields(spec))
>     {
>         result.addField(field.name, field.type)?
>     }
>     return result;
> }
> ---
>
> or how is it supposed to look? I'd figure compile times will be 
> improved greatly at first and suffer heavily afterwards, 
> because everyone will be using this awesome feature to do even 
> more at compile time.
>
> Is there any plan to cache the results of type functions? What 
> do we need to incorporate into the design to make it cacheable?
>
>
> I am eager to see this in action.

struct from spec is exactly one of the things that will not be 
possible without wrapping it in a template.

template structFromString(string spec)
{
     alias structFromStringTypeFn(string spec)
     {
         ...
     }
     alias = structFromString = structFromStringTypeFn!(spec);
}
that looks a bit strange but it allows me to not have to worry 
about certain constraints that I would otherwise have to worry 
about.