Do string mixins work under -betterC?

[DLearner]

On Tuesday, 16 December 2025 at 20:56:06 UTC, Richard (Rikki) 
Andrew Cattermole wrote:
> On 17/12/2025 9:48 AM, DLearner wrote:
>> I have a rather complicated string mixin defined and invoked 
>> from within the same source file.
>> Which seems to work.
>> 
>> But when I move the mixin definition to a separate module, and 
>> import that module into the original source file, the 
>> compilation collapses complaining that array concatenation 
>> requires the GC, which is not available with -betterC.
>> 
[...]

> string genStuff(string val) {
> 	return val ~ ";";
> }
>
> void myFunc() {
> 	mixin(genStuff("this"));
> }
> ```
>
> This won't work without a way to mark `genStuff` as CTFE only. 
> Which doesn't exist currently.
>
> Compiler has to know that a given execution context is CTFE 
> only otherwise disallowed.

1. Any proposals to mark a function as CTFE only?
2. Why (and I've now got this down to a cut-and-paste) is there 
no problem if the mixin definition is in the main function, but 
problem appears if the definition is moved to a separate module 
(which is imported into the main function)?

DL