#13546: Kind error with type equality -------------------------------------+------------------------------------- Reporter: int-index | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 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: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Not quite. `UnT` really has kind `pi k. Type -> k`, because the `k` can be used in pattern-matching. The behavior of `UnT` is to reduce only when the (invisibly) provided `k` matches the kind of the argument of `T`. Unlike when defining ordinary functions, polymorphism in type families is ''not'' parametric. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13546#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler