> There is meta-programming with annotations:

There is, but your example is not valid. You can't use short function syntax in constant expressions, it has to be an explicit `static function`.

The reason for this, IIRC (I can't find the GitHub issue or PR atm) is that these functions aren't allowed to close over any variables, and with fn syntax doing so is implicit. Rather than erroring they've disallowed the use of arrow functions entirely.