#13735: RankNTypes don't work with PatternSynonyms -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: invalid | Keywords: | PatternSynonyms 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 Iceland_jack): A coworker at work helped me reach this {{{#!hs newtype A = A (forall xx. xx -> xx) newtype Endo a = Endo { appEndo :: a -> a } newtype B = B (forall xx. Endo xx) pattern PatB :: (forall xx. xx -> xx) -> B pattern PatB f <- ((\(B f) -> A (appEndo f)) -> A f) where PatB f = B (Endo f) }}} which works, similarly with `PLambda` {{{#!hs data PLambda a = Lam { unLam :: a -> PLambda a } | ... newtype LAM = LAM (forall xx. xx -> PLambda xx) newtype Lam = L (forall a. PLambda a) get :: Lam -> LAM get (L f) = LAM (unLam f) pattern LLAM :: (forall a. a -> PLambda a) -> Lam pattern LLAM f <- (get -> LAM f) where LLAM f = L (Lam f) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13735#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler