#8196: Core Lint error in Specialise with PolyKinds and derived instance -------------------------------------------------+------------------------- Reporter: adamgundry | Owner: Type: bug | simonpj Priority: normal | Status: new Component: Compiler | Milestone: Resolution: | Version: 7.7 Operating System: Unknown/Multiple | Keywords: Type of failure: Incorrect warning at | Architecture: compile-time | Unknown/Multiple Test Case: | Difficulty: Blocking: | Unknown | Blocked By: | Related Tickets: -------------------------------------------------+------------------------- Comment (by adamgundry): I realised that this may be nothing to do with '''deriving''', as a hand- written instance causes the same problem: {{{ instance forall (a :: k -> *)(b :: k) . Show (a b) => Show (T a b) where show (MkT x) = show x }}} On the other hand, everything works if one removes the kind polymorphism: {{{ instance forall (a :: * -> *)(b :: *) . Show (a b) => Show (T a b) where show (MkT x) = show x }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8196#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler