Richard Eisenberg <e...@cis.upenn.edu> writes: > Yes, I believe that's right. As far as I can figure out, these classes > really *are* problematic, in that if we allowed > GeneralizedNewtypeDeriving for them, there would be a way to subvert > the type system. To make these derivable, we would need to be able to > restrict various type parameters from taking on values that take a > nominal argument. Without the ability to restrict the values in this > way, there could be trouble. > I suppose it's unlikely that the roles mechanism will be extended to allow for such restriction?
Cheers, - Ben
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