My guess is that you need `mixin` to have the symbol lookup happen later, but I'm not familiar with that part of the language.
`mixin` is mentioned here [https://nim-lang.org/docs/manual.html#generics-symbol-lookup-in-generics](https://nim-lang.org/docs/manual.html#generics-symbol-lookup-in-generics) but there isn't a lot of documentation.
