[GHC] #14579: GeneralizedNewtypeDeriving produces ambiguously-kinded code

[GHC]

#14579: GeneralizedNewtypeDeriving produces ambiguously-kinded code
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.2
  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):  Phab:D4264
       Wiki Page:                    |
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Comment (by goldfire):

 Ryan's visit to panictown notwithstanding, I'm still not convinced by
 comment:5. comment:5 seems to be suggesting that we need the generated
 code to pass through the renamer, so that the type variables can be
 captured. This is a reasonable guess. But `typeToLHsType`, as currently
 written (and working), uses `Exact` names, so the journey through the
 renamer doesn't capture anything. Perhaps the panic is actually caused by
 these lines in !RnTypes:

 {{{#!hs
 rnHsTyKi _ (HsCoreTy ty)
   = return (HsCoreTy ty, emptyFVs)
     -- The emptyFVs probably isn't quite right
     -- but I don't think it matters
 }}}

 Maybe it matters. Or maybe I'm missing something more fundamental.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14579#comment:7>
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