#8020: Closed type families break substitution -----------------------------+---------------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.7 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- This code causes a Core Lint error: {{{ {-# LANGUAGE TypeFamilies #-} type family F a b where F (Maybe a) [a] = Int F b c = Bool data Proxy a = P type family G foo :: Proxy d -> F d d -> Bool foo _ = not bar :: Bool -> Bool bar = foo (P :: Proxy G) }}} The solution needs to freshen variables before doing apartness checking. I will fix in due course. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/8020 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler