#14861: QuantifiedConstraints: Can't use forall'd variable in context -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: 8.5 checker) | Keywords: Resolution: invalid | 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: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: new => closed * resolution: => invalid Comment: Hm. Your point about `instance C a => C [b]` being wonky is a good one. In practice, such an instance would probably be OK if we could explicitly manipulate dictionaries and specify what exactly `a` should be whenever we applied it. But alas, we cannot, and GHC is unwilling to do this for us, so I'm forced to agree that this is in the realm of the impossible for the time being. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14861#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler