Compiler-recognized template patterns

[Richard (Rikki) Andrew Cattermole]

On 23/07/2024 9:36 PM, Quirin Schroll wrote:
>  From [D Language Foundation March 2024 Monthly Meeting 
> Summary](https://forum.dlang.org/post/qwyhlvqintqsnzwnzuwv@forum.dlang.org)
>> Walter said the way to do that was to have the compiler recognize the 
>> template and not instantiate it, but just return the result. He'd done 
>> that for a couple of the templates. `Unqual` sounded like a good 
>> candidate for that. Then it would still look like a template, but it 
>> wouldn't have the cost of a template anymore.
> 
> That’s not a good solution, it’s just whack-a-mole. Why not add a pragma 
> so that any template can be like that at the programmer’s discretion? 
> `pragma(nocache)` or something like that. We can add it to any Phobos 
> template and D programmers can add it in their code bases where they see 
> fit.

Turning off caching requires template instantiation to occur. It does 
not change that.

The point is to recognize a template instantiation request as a 
``__trait`` which is very cheap to do on the compiler side.

So no, turning off caching wouldn't be beneficial.