SomeString fizzbar(RandomAccessRange!SomeNumeric r) {...}
Looks like concepts.We've settled on leveraging the already useful template constraints (at best in CNF [¹]) for better error messages. It's on the Agenda for later this year [²].
[¹]: https://github.com/dlang/phobos/pull/5461 [²]: https://wiki.dlang.org/Vision/2017H2_draft
