I meant impossible to do statically, of course it's possible to check instance
type at runtime.
proc some(parent: Parent): void =
# impossible to determine if parent has specific child type at compile
time
Run
compared to
proc some(child: Child): void =
# trivial to cast to Parent
let parent: Parent = child
Run
So, it's trivial to go in one direction, and impossible to go (at compile time,
when compiler works) in another.
