#7939: RHS of associated type not kind-checked ------------------------------------------+--------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHC accepts invalid program | Difficulty: Unknown Testcase: ghci/scripts/T7939 | Blockedby: Blocking: | Related: ------------------------------------------+--------------------------------- Comment(by monoidal): I think it's fine to default to *. But, again, consider {{{ type family A :: k type instance A = Double type instance A = Maybe }}} Should this really compile? I don't know, it looks suspicious but perhaps it is OK. What makes me suspicious is this. Consider {{{ data D :: k -> * where D1 :: D Bool D2 :: D Maybe }}} GHC gives an error: {{{ Data constructor `D1' cannot be GADT-like in its *kind* arguments D1 :: D * Bool }}} But this seemingly equivalent code compiles: {{{ {-# LANGUAGE TypeFamilies, GADTs, PolyKinds #-} type family A :: k type instance A = Bool type family B :: k type instance B = Maybe data D :: k -> * where D1 :: D A D2 :: D B }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7939#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler