#15347: QuantifiedConstraints: Implication constraints with type families don't work -------------------------------------+------------------------------------- Reporter: aaronvargo | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.5 checker) | Keywords: Resolution: | QuantifiedConstraints 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 goldfire): I don't see how this is different from #14860. It looks the same to me. But I think `(x ~ F b, forall a. a => x)` and `forall a. a => F b` really are different. It's all about shadowing. The first casts a much bigger shadow, one whose shape can be specified. The second's shadow is too oddly shaped to be predictable. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15347#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler