#8883: FlexibleContexts checking should happen also on inferred signature -------------------------------------+------------------------------------ Reporter: Blaisorblade | Owner: jstolarek Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by jstolarek): Replying to [comment:1 simonpj]:
if someone would like to have a go it would not be hard and I could offer guidance. I'd like to tackle this one. Guidance will be really appreciated.
I reduced the test case to this snippet of code: {{{ {-# LANGUAGE TypeFamilies, DeriveFunctor, NoMonomorphismRestriction #-} -- , FlexibleContexts module T8883 where type family PF a :: * -> * class Regular a where from :: a -> PF a a -- But in fact, the construction is just an instance of fold. --fold :: (Functor (PF a), Regular a) => (PF a b -> b) -> a -> b fold f = f . fmap (fold f) . from }}} So how should GHC behave for this code? Reject it because !FlexibleContexts extension is not enabled? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8883#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler