Hi devs, between ghc-7.11.20150215 and ghc-7.11.20150407 I experienced a strange regression with deriving Typeable for data with Nat-kinded indices. Something like this used to work (I cannot post the whole thing, unfortunately) {{{ data OTU (p :: Nat) (o :: Nat) = OTU { ...fields... } deriving (Show, Typeable) }}} With my ghc-7.11.20150407 (and later) strange obligations of the form `Typeable p` appear, rendering my code uncompilable. But there is no way I can see how I can convince the type checker that the Nat index is indeed Typeable. I *do* have a `KnownNat p` constraint around, though. The relevant changes to mainline appear to be https://github.com/ghc/ghc/commit/b359c886cd7578ed083bcedcea05d315ecaeeb54 https://github.com/ghc/ghc/commit/3a0019e3672097761e7ce09c811018f774febfd2 both by Iavor. So now my questions: 1) Is this a regression on mainline? (I surely hope so!) How did this work before? 2) Should `KnownNat p` imply `Typeable p` for the ability to have my `Typeable (OTU p o)` 3) if 2) is answered with "NO", how am I supposed to satisfy those constraints? Thanks and cheers, Gabor PS: Sometimes I feel like a canary doing my research-like programming with GHC-HEAD, and it is a mostly positive experience, but events like this make me shiver...