#12922: Kind classes compile with PolyKinds -------------------------------------+------------------------------------- Reporter: Tritlo | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I was asking around on #haskell to better understand the new language extension, -XTypeInType, and how it is different from -XPolyKinds. To study it, I was working with the following small example: {{{ {-# LANGUAGE TypeFamilies, GADTs, TypeOperators, DataKinds, PolyKinds #-} module Main where import Data.Kind (Type) -- Define a Type for the natural numbers, Zero and a successor data Nat = Z | S Nat class Addable k where type (a :: k) + (b :: k) :: k instance Addable Nat where type (Z + a) = a }}} (for more context, see https://gist.github.com/Tritlo/ce5510e80935ac398a33934ee47c7930) Since according to a responder on #haskell, the ability to have kind classes required TypeInType, and should not work with PolyKinds. As the documentation mentions that there could be leakage between PolyKinds and TypeInType and to report such leaks, I felt that I should report it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12922 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler