On Apr 11, 2016, at 6:39 PM, Simon Peyton Jones <simonpj at microsoft.com> wrote: > It's _nothing_ to do with whether the kind changes! > > It's everything to do with cloning the binder if it is already in scope. See "Secrets of the GHC inliner", the section called "The rapier", I think. Ah yes. Silly me. Thanks, Richard