#14734: QuantifiedConstraints conflated with impredicative polymorphism? -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.5 Resolution: invalid | 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: | -------------------------------------+------------------------------------- Changes (by simonpj): * status: new => closed * resolution: => invalid Comment:
it is considered impredicative polymorphism, but is it?
Yes it is. You are instantiating a type variable (the `a` from `newtype a :- b`) with a polymorphic type. I think you need impredicativity here. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14734#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler