#14331: Overzealous free-floating kind check causes deriving clause to be rejected -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.2.1 checker) | Resolution: | Keywords: deriving Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | deriving/should_compile/T14331 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I posted this to a branch instead of Phab per SPJ's request, since he says he finds that easier to navigate to Phab. As far as `newMetaTyVars` goes: yes, I'm aware that I needn't call `newMetaTyVars` on //everything// in `tvs`. As I mentioned, I'm taking this piece-by-piece, and I wanted to get the simple case where the `deriving` clause mentions no variables working first before I add additional complexity on top (especially since the simple case is proving to be so difficult). I still need the `tcUnifyTy` because of this validity check: https://github.com/RyanGlScott/ghc/commit/d8ed9e57ecc60a78321ab10b02f6387759... #diff-6ce1356ff43cc56932867d6f6b63d7dcR718 I'm quite confused at all the different variants of of `zonkWibbleWobble` out there. There's `zonkTcType` and `zonkTcTypeToType` for starters (whose simultaneous existence still baffles me), and now there's `zonkQuantifiedTyVar` and `zonkTyBndrX`‽ How is someone like me who isn't in the loop supposed to be able to discern all of these little idiosyncrasies? (Sorry, rant over. I frequently get overwhelmed at all of the arcane knowledge one needs to make simple changes to the typechecker.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14331#comment:49 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler