[GHC] #14175: Panic repSplitTyConApp_maybe

[GHC]

#14175: Panic repSplitTyConApp_maybe
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.2
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13910            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I'm confused about what this fix is doing. Isn't `k` implicitly
 quantified? In other words, what does your patch do on this program, which
 explicitly quantifies `k` but throws the same panic?

 {{{#!hs
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeInType #-}
 module Bug where

 import Data.Kind

 class C a where
   data CD k (a :: k) :: k -> *

 instance C (Maybe a) where
   data CD k (a :: k -> *) :: (k -> *) -> *
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14175#comment:4>
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