I have to ask: how did you figure that out? I don;t see anything in the error message (nor in the code) that would suggest PolyKinds are causing
#9103: hackage's type-level-0.2.4 fails to compile -------------------------------------+------------------------------------- Reporter: slyfox | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.2 checker) | Keywords: Resolution: invalid | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: #8634 | -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:10 jstolarek]: the problem. I was just trying to figure out what could possibly be different between the two cases. With !PolyKinds on, the empty-datatype method produces an extra degree of freedom, in the kind of the parameter to `Succ`. Seeing nothing else which could be causing difficulty, I thought !PolyKinds would have to be the problem. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9103#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler