#12088: Type/data family instances in kind checking -------------------------------------+------------------------------------- Reporter: alexvieth | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #11348, #12239, | Differential Rev(s): Phab:D2272 #12643, #13790 | Wiki Page: | https://ghc.haskell.org/trac/ghc/wiki/GhcKinds/KindInference| -------------------------------------+------------------------------------- Comment (by goldfire): Iavor asked on the mailing lists about this example: {{{#!hs {-# Language TypeInType, TypeFamilies #-} module Help where import Data.Kind type family IxKind (m :: Type) :: Type type family Value (m :: Type) :: IxKind m -> Type data T (k :: Type) (f :: k -> Type) type instance IxKind (T k f) = k type instance Value (T k f) = f }}} Currently, you have to put a `$(return [])` between the two instances to get GHC to accept. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12088#comment:44 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler