Reading the [new style concepts RFC](https://github.com/nim-lang/RFCs/issues/168), we see that the first goal is Empower concepts to make generic code type-checkable at declaration time, not only at instantiation time. Run
>From that we can draw some hope that this particular omission in Nim concepts >will be addressed. It would be pretty cool if Nim concepts handle this better >than C++ 20, though I don't know if that is how C++ 20 is supposed to behave, >I just compiled it with `clang++ --std=c++20` to check. BTW, nice example! I hope you file an issue.
