Ah! I meant to write decltype(x). And indeed you are right, it is int. TIL. I had checked on godblot, but of course the typo misled me. In retrospect it makes

Ah! I meant to write decltype(x). And indeed you are right, it is int. TIL. I had checked on godblot, but of course the typo misled me. In retrospect it makes sense, there is no operator| for enum, it is just calling the int version after implicit conversion.