#13998: Default Signature messes up arity of type constructor -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: 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): Woo, Simon to the rescue! Out of curiosity, are you trying to fix this by changing the visibility of `k`, or changing the codegen to spit out `$dmeqForallPoly @Atom @Value` instead? The former fix sounds more principled, but I think harder, since it seems that GHC doesn't track visibility for class tyvars like I would have imagined: {{{ λ> :type +v eqForallPoly eqForallPoly :: forall k (f :: k -> *). EqForallPoly f => forall (a :: k) (b :: k). f a -> f b -> Bool }}} I would have expected instead: {{{ λ> :type +v eqForallPoly eqForallPoly :: forall {k} (f :: k -> *). EqForallPoly f => forall (a :: k) (b :: k). f a -> f b -> Bool }}} But this should probably go in a separate ticket. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13998#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler