#9858: Typeable instances should be kind-aware -------------------------------------+------------------------------------- Reporter: dreixel | Owner: dreixel Type: bug | Status: new Priority: highest | Milestone: 7.10.1 Component: Compiler | Version: 7.9 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by dreixel): Replying to [comment:24 simonpj]:
One drastic remedy: do not derive `Typeable` for polykinded type constructors. That would be easy to implement, and would certainly fix it. But it's a bit drastic.
Isn't that very drastic? So a data constructor that is declared with `PolyKinds` on, but can be used without it (such as `Proxy`), won't be allowed to have a `Typeable` instance at all? Or would we allow a (orphan) `Typeable` instance to be derived in a module that does not have `PolyKinds` on? Even if so, I'm afraid this might have important ramifications, also given that SYB requires `Typeable`... How about just marking `Typeable` instances for polykinded type constructors as Unsafe (if that's possible)? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9858#comment:25 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler