[GHC] #14331: Overzealous free-floating kind check causes deriving clause to be rejected

[GHC]

#14331: Overzealous free-floating kind check causes deriving clause to be rejected
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        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:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"82b77ec375ab74678ac2afecf55dc574fa24490f/ghc" 82b77ec/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="82b77ec375ab74678ac2afecf55dc574fa24490f"
 Do not quantify over deriving clauses

 Trac #14331 showed that in a data type decl like

    data D = D deriving (C (a :: k))

 we were quantifying D over the 'k' in the deriving clause.  Yikes.

 Easily fixed, by deleting code in RnTypes.extractDataDefnKindVars

 See the discussion on the ticket, esp comment:8.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14331#comment:10>
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