#14860: QuantifiedConstraints: Can't quantify constraint involving type family -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: 8.5 checker) | Keywords: Resolution: wontfix | QuantifiedConstraints wipT2893 Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): An example, from [https://www.microsoft.com/en-us/research/wp- content/uploads/2016/02/jfp-outsidein.pdf OutsideIn(X)] (**2.4**), this function {{{#!hs h :: forall a. (forall b. FB a b ~ Bool) => Bar a -> Bool }}} Details in [https://gist.github.com/Icelandjack/aeda8e98214cc52c96230af7b8724d25 gist]. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14860#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler