#8913: either bug or confusing error message mixing PolyKinds and TypeFamilies -------------------------------------+------------------------------------- Reporter: ghorn | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.1-rc2 checker) | Keywords: PolyKinds, Resolution: | TypeFamilies Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------- Comment (by goldfire): With `-fprint-explicit-kinds` we see that this really looks like a proper inference bug: {{{ Could not deduce (GCat * (MyRep a)) arising from a use of ‘gcat’ from the context (GCat * (MyRep a), MyGeneric a) bound by the type signature for cat :: (GCat * (MyRep a), MyGeneric a) => a -> Int at Scratch.hs:12:8-48 In the expression: gcat (from x) In an equation for ‘cat’: cat x = gcat (from x) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8913#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler