join does not use ADL on begin/end of its ranges

[rhalbersma]

fmt::join is using std::begin and std::end on the range it is being passed. This makes it harder for user-defined types that have their own begin and end living in their own namespace. E.g., range-for does ADL on begin/end on a range's associated namespaces. It it by design that {fmt} does not do the same?

[vitaut]

It it by design that {fmt} does not do the same?

Not really, just an implementation artefact. A PR to add ADL support is welcome.