Nimrod features distinct types (http://build.nimrod-lang.org/docs/manual.html#distinct-type http://build.nimrod-lang.org/docs/manual.html#distinct-type) which a

Nimrod features distinct types (http://build.nimrod-lang.org/docs/manual.html#distinct-type http://build.nimrod-lang.org/docs/manual.html#distinct-type) which allow you to implement something like this. Here is an example: https://github.com/def-/units/blob/master/units.nim#L220 https://github.com/def-/units/blob/master/units.nim#L220, I don't think it's complete yet though.