"Error: `TypeInfo` cannot be used with -betterC" on a CTFE function

[Liam McGillivray]

On Monday, 8 April 2024 at 08:12:22 UTC, Richard (Rikki) Andrew 
Cattermole wrote:
>>> ```d
>>> template Foo(Args) {
>>>     enum Foo = () {
>>>         return Args.init;
>>>     }();
>>> }
>>> ```
>>>
>>> Something like that should work instead.
>> 
>> I'm sorry, but I can't comprehend any of your example. What 
>> would be fed into `Args`? I don't understand how this works, 
>> or how I would use it for what I want.
>
> You would replace it with whatever template parameters you want 
> (including nothing). It's there as a place holder.
>
> Same for the return on the closure.
>
> But the main thing to understand is that the closure that gives 
> the enum a value, that'll be CTFE only, no runtime target.

Are you saying that this is a way to guarantee that the code is 
compile-time only?

I still understand very little of this code. I'm not experienced 
in D metaprogramming; just the function I posted above was a 
major achievement for me. I don't understand how I would use the 
code you gave in place of the function I have written and posted 
above.

When you say that "You would replace it with whatever template 
parameters you want", are you saying that instead of doing 
`mixin(MakeStringOverload!SetWindowTitle); 
mixin(MakeStringOverload!LoadShader);` as posted above, I would 
write `mixin(Foo!(SetWindowTitle, LoadShader));`?

What does the `return Args.init;` line mean in your example? Am I 
supposed to replace this with a call to the CTFE function I had 
already written? If so, it didn't work. Making such a replacement 
resulted in the same "TypeInfo" error that I had already.