String interpolation, after a healthy debate on discord

[WebFreak001]

On Tuesday, 14 December 2021 at 11:02:58 UTC, Ogi wrote:
> On Tuesday, 14 December 2021 at 09:35:27 UTC, WebFreak001 wrote:
>> no this proposal does not suggest moving any functionality 
>> into the compiler. It suggests to add the istrings (tuples 
>> with header) as described in the YAIDIP and have special 
>> function calling syntax (`functionName"istring contents"`) 
>> that will call any function, that accepts an istring as only 
>> argument.
>
> I was referring to YAIDIP. According to it, istring should be 
> allowed in `mixin`, `pragma(msg)` and `assert` (missed this 
> one). This requires reimplementing `text` in the compiler.

ah right you mean for the built-in istring usage in the compiler 
it needs to be implemented.

I don't think it's such a big problem though, as the phobos 
implementation would also just be: (a little simplified)

```d
auto text(istring...)(istring s) if (isIString!istring)
{
     return text(s[1 .. $]); // removes special __header, just 
concatenate rest
}
```