On Thu, 2009-04-09 at 19:13 +0900, Jacques Garrigue wrote:
> This may be a bit confusing, but the .. in your constraint on 'c means
> that no actual subtyping will occur when you use this type as target.
> Indeed, if the constraint was left unchanged, it would mean that by
> choosing an arbitrary instance, you could use the as_c method to
> convert an object of type "t a" to any "t".
Why it can't be converted to any valid "t"?