#14799: QuantifiedConstraints: Problems with Typeable -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 Resolution: | Keywords: | QuantifiedConstraints, wipT2893 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): So your first example didn't compile for me: {{{ Bug.hs:9:31: error: parse error on input ‘@’ | 9 | a (MkEx (_::xx)) = typeRep @_ @xx Proxy | ^ }}} So I added `TypeApplications`: {{{#!hs {-# Language GADTs, ConstraintKinds, ScopedTypeVariables, QuantifiedConstraints #-} {-# Language TypeApplications #-} import Data.Typeable data Ex cls where MkEx :: cls xx => xx -> Ex cls a :: Ex Typeable -> TypeRep a (MkEx (_::xx)) = typeRep @_ @xx Proxy b :: (forall xx. cls xx => Typeable xx) => Ex cls -> TypeRep b (MkEx (_::xx)) = typeRep @_ @xx Proxy c :: (forall xx. cls xx => Show xx) => Ex cls -> String c (MkEx xx) = show xx }}} And now it compiles! So I'm not sure what you're doing differently. (Please make sure you've given us all the language extensions/flags you're using—it makes a huge difference!) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14799#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler