#8917: :kind! does not work under type constructors ------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.8.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Say I have the following: {{{ {-# LANGUAGE DataKinds, PolyKinds, TypeFamilies #-} module Scratch where data Nat = Zero | Succ Nat type family a + b where Zero + a = a (Succ n) + m = Succ (n + m) }}} I load this into ghci. See what happens next: {{{ GHCi, version 7.8.0.20140228: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Scratch ( Scratch.hs, interpreted ) Ok, modules loaded: Scratch. *Scratch> :kind! Zero + Succ Zero Zero + Succ Zero :: Nat = 'Succ 'Zero *Scratch> :kind! Succ (Zero + Zero) Succ (Zero + Zero) :: Nat = 'Succ ('Zero + 'Zero) }}} Note the last line. It doesn't reduce under the `Succ`! I will fix shortly. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8917 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler