literals larger than int32 automatically promoted to int64, otherwise they use type int (32-bit or 64-bit depending on the platform).
int64 literals can't be converted to uint64 type. So a workaround is to specify the type of literal with `'u64` so conversion is not needed. Related: * <https://github.com/nim-lang/Nim/issues/14522> * <https://github.com/nim-lang/Nim/pull/14530>
