#10760: Conflicting typefamily instances not reported with polykinds -------------------------------------+------------------------------------- Reporter: steely | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by goldfire): * status: new => closed * resolution: => invalid Comment: This is correct behavior. All kind variables in a type family are always inputs. This is admittedly counter-intuitive when the kind variable classifies the result. If we write kinds explicitly, your example becomes this: {{{ type family Bar k (a :: *) :: k type instance Bar * Int = Int type instance Bar (* -> *) Int = [] }}} If you have a concrete suggestion of how to improve the manual in this regard, we'd love to have it. Thanks for reporting! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10760#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler