I just discovered that bloody Haskell has a LANGUAGE directive that runs the file through the bloody C preprocessor, so it seems safe to say that while it is often pretty cursed, conditional compilation is one of those things where if you don't do it, someone else will do it for you and badly.

So idk exactly what form this will take --maybe just a macro?-- but you can bet your ass it will be a core feature.

Seriously. cpp. Literally any templating language is better than that.