String interpolation, after a healthy debate on discord

[deadalnix]

On Thursday, 9 December 2021 at 21:06:11 UTC, WebFreak001 wrote:
> The simpler syntax would be an additional special function 
> calling syntax (only valid for functions accepting the 
> interpolated strings with the header as suggested by YAIDIP)
>
> Example:
> ```d
> string text(T...)(T args) if (isInterpolatedString!T) { ... }
>
> // could then be called:
>
> text"Hello $name!";
>
> // translates to:
> text(i"Hello $name!");
>
> // translates to:
> text(InterpolationHeader!("Hello ", "name", "!"), "Hello ", 
> name, "!");
> ```
>

This is much better. You'll note that the `i""` doesn't need to 
be backed in the language anymore with that construct and can be 
written as a library, if you define the rewrites the other way 
around.