Discussion Thread: DIP 1036--String Interpolation Tuple Literals--Community Review Round 2

[Q. Schroll]

On Thursday, 4 February 2021 at 18:14:59 UTC, Q. Schroll wrote:
> Formally, the compiler has to try the __interp and the string 
> version. If both succeed (that's the relevant case) and 
> instantiate THE SAME template, the string version (i.e. idup) 
> will be used. Otherwise, the __interp is a better match and 
> will be used.

I want to add how this works when using interpolated strings as 
template parameters. If templ is a template, templ!i"Hello 
${name}, it's me!", also both rewrites are tried. If the only 
template is like this

     template templ(args...) { ... }

it will make args.length == 1 and args[0] == "Hello "~name~", 
it's me!". To match an interp sequence, one needs an overload 
like this

     template templ(args...)
         if (args.length > 0 && is(typeof(args[0]) == interp!str, 
string str))
     { ... }

that matches no string, but an interp object. The case is 
relevant because one might want to handle the parts specially 
even though @nogc and stuff is no concern for compile-time 
constructs.
The same as aforementioned, you cannot have one template that 
fits all and decides later.