I’m wondering where you wanted to use this. Was it a generic context, where you didn’t know what types you were getting? Also, I think it will interfere with the retern-value optimization.

I saw a commit for it, but I don’t think it’s released… So “the next one” probably. Same story with applying to all modes. More details on my answer here.

Yay! The static_assert(false) thing was resolved as no longer ifndr.