I am not an expert in concepts, but I would assume as it's experimental feature a lot of things don't work. As for docs the RFC you linked might be the only place they're documented right now. But there's also an older variant that's has received more [work](https://nim-lang.github.io/Nim/manual_experimental.html#concepts)
Imo you're better off using plain generics, you don't need any type specialization for them to work.
