Hello! I was testing some Nimble packages with ARC, and found out that your package fails tests with ARC. It turned out that the cause is simple - you're relying in repr which behaves differently for ARC.

I suggest you to consider not using repr at all (since it's really only for humans and isn't supposed to be parsed programmatically), or at least fix it for ARC (and ORC which will probably become the default in 1.4), the simplest possible fix being:

      runedAlphabet.repr[0 .. ^(when defined(gcArc): 1 else: 2)].split("@".runeAtPos(0), 1)[1] &

on line 314 in nbaser.nim