[Issue 20012] export inside mixin doesn't seem to work

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20012

--- Comment #20 from Dennis <dkorpel at live.nl> ---
(In reply to anonymous4 from comment #16)
> Callbacks are more common than reflection-based dll exports. 

Dplug has them:
https://github.com/AuburnSounds/Dplug/blob/5ad0e4c512299fe8ea811ef2b041829f22f02a51/client/dplug/client/dllmain.d#L59

Excel-d has them:
https://github.com/kaleidicassociates/excel-d/blob/ea7eb514e39e91fbc637e71a90d72614698dac18/source/xlld/wrap/traits.d#L234

It even mentions how "This used to be a template mixin but even using a string
mixin inside fails to actually make it an extern(C) function.".

Can you give an example where the proposed behavior would be problematic?

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