Templates with scope

[bauss]

On Wednesday, 21 July 2021 at 09:06:52 UTC, Sönke Ludwig wrote:
> Am 21.07.2021 um 09:16 schrieb bauss:
>> Is there a way to make this logic work without using a mixin 
>> template.
>> 
>> I'd prefer if using a plain template was possible, rather than 
>> using a mixin template, because it introduces some extra 
>> boilerplate.
>
> The symbol name is not available in the scope of the template, 
> so that the `mixin(symbol.stringof)` doesn't work, but you can 
> simply use the alias directly:
>
>     template CanCompile(alias symbol)
>     {
>         enum CanCompile = __traits(compiles, { symbol = 10; });
>     }

The problem is that I just saw I didn't describe my problem very 
well, as I don't actually have the symbol at the given time.

I only had the symbol name and I use it to test if the symbol is 
available because it comes from a __traits(allMembers) which 
includes some symbols that makes it fail to compile if I try to 
use the symbol directly without checking whether it compiles or 
not.

And this was the exact template I was trying to use:

```d
template CanUseSymbol(string symbolName, string symbolAlias = 
"symbol", string moduleAlias = "moduleImport")
{
   enum CanUseSymbol = __traits(compiles, { mixin("alias " ~ 
symbolAlias ~ " = " ~ moduleAlias ~ "." ~ symbolName ~ ";"); });
}
```

For obvious reasons it doesn't work as you also mentioned, the 
scope simply isn't available.

But I can't use alias unfortunately in this case.

I wish there was a way to return the symbols from allMembers, 
instead of just the name of the symbols, that would solve this 
problem.