Sadly C’s `_Generic` typecase mechanism does not do SFINAE: all the branches have to typecheck OK, regardless of which one is selected. This is OK for <tgmath.h> where the cases are different sizes of float, where there are few opportunities to get different failures in the different cases, but it makes _Generic hard to use for more template-like code.

Given how hard SFINAE is to understand for typical developers, I consider it a good thing, actually.

Sure, but I’m not aware of them being used in any significant capacity, so I don’t think it’s particilary pertinent to this discussion.

Ah, in that regard you are right, I guess.