#13895: "Illegal constraint in a type" error - is it fixable? -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): Interesting. Simon once [https://mail.haskell.org/pipermail/ghc- devs/2016-September/012824.html commented] that using `TypeApplications` to call a polymorphic function at a polymorphic type fell under a safe subset of `ImpredicativeTypes` (that ought not require bringing in the other baggage that `ImpredicativeTypes` implies). If we had this capability, would `Typeable @(forall k. k -> Type) t` be a thought GHC could think? (I realize that we don't yet have visible kind applications, but you get the idea.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13895#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler