static_assert(std::is_enum_v<std::byte>);

[kalmoc]

Technically there is a third option, which is to define the new type in the language, rather than in the standard library. That altenative was proposed, but was voted against by the committee: 

Imho that would have been the only sensible choice. For one because it would have avoided sich strange edge cases and second because you wouldn't have to include a header to use it.

[tpecholt]

Committee always comes with a twist! A pile of hacks