#14331: Overzealous free-floating kind check causes deriving clause to be rejected -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.2.1 checker) | Resolution: | Keywords: deriving 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 assume you really meant {{{#!hs data D = D deriving (forall k a. C (a :: k)) }}} but that GHC doesn't quantify `k` the right way. So it's a bug in kind quantification, not the free-floating kind variable check. (Sidenote: that `forall` isn't allowed there. But perhaps it should be incorporated into [https://github.com/ghc-proposals/ghc- proposals/blob/master/proposals/0007-instance-foralls.rst the recent proposal expanding where `forall` can be used.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14331#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler