#11084: Some type families don't reduce with :kind! -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: TypeFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I've trimmed down this example even more: {{{#!hs {-# LANGUAGE TypeFamilies #-} module T11084Aux where type family F a type instance F a = Int }}} {{{#!hs {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE UndecidableInstances #-} module T11084 where import T11084Aux type family G where G = F Char }}} Moreover, `cabal new-build` makes it much easier to reproduce this bug than it used to be. Now all you have to do is this: {{{ $ git clone https://github.com/RyanGlScott/ghc-t11084 $ cd ghc-t11084/ $ cabal new-build -w /opt/ghc/8.6.3/bin/ghc $ /opt/ghc/8.6.3/bin/ghci -package-env .ghc.environment.x86_64-linux-8.6.3 GHCi, version 8.6.3: http://www.haskell.org/ghc/ :? for help Loaded package environment from .ghc.environment.x86_64-linux-8.6.3 Loaded package environment from .ghc.environment.x86_64-linux-8.6.3 Loaded GHCi configuration from /home/rgscott/.ghci λ> import T11084 λ> :kind! G G :: * = ghc-t11084-0.1:T11084Aux.F Char λ> :kind! G G :: * = Int }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11084#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler