#12381: Type family not reduced -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 8.0.1 (Type checker) | 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: -------------------------------------+------------------------------------- Andres pointed out that the following fails to compile with GHC 8.0.1 but succeeds with `master` (f53d761df9762232b54ec57a950d301011cd21f8), {{{#!hs {-# LANGUAGE TypeInType, TypeFamilies #-} module Kinds where import GHC.Types type family G (a :: Type) :: Type type instance G Int = Bool type family F (a :: Type) :: G a type instance F Int = True }}} Error: {{{ Hi.hs:10:23: error: • Expected kind ‘G Int’, but ‘'True’ has kind ‘Bool’ • In the type ‘True’ In the type instance declaration for ‘F’ }}} We should figure out what fixed this so it can hopefully be merged for 8.0.2. I initially suspected the patch cited in #12175 but sadly this doesn't seem to be the case. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12381 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler