#11719: Cannot use higher-rank kinds with type families -------------------------------------+------------------------------------- Reporter: ocharles | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler (Type | Version: 8.0.1-rc2 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | dependent/should_compile/T11719 Blocked By: | Blocking: Related Tickets: #13913 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): These two declarations have quite different meanings: {{{#!hs type family F1 :: k -> Type type family F2 :: forall k. k -> Type }}} `F1` takes one argument, `k`. `F2`, on the other hand, takes no arguments. `F1` can match on `k`, returning constructors of different kinds in different instances. On the other hand, `F2` must return a polykinded constructor, and can have only one instance. So, I think this is unrelated to the ticket... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11719#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler