[GHC] #14880: GHC panic: updateRole

[GHC]

#14880: GHC panic: updateRole
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.2
  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:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Replying to [comment:6 goldfire]:
 > With the `Foo` in comment:3, this also panics:

 It does? I must be doing something wrong, since this appears to compile
 for me:

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

 import Data.Kind
 import Data.Proxy

 data Foo (x :: Type) :: forall (a :: x). Proxy a -> Type

 quux :: forall x arg. Proxy (Foo arg) -> Maybe x
 quux = undefined
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880#comment:7>
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