[GHC] #12083: ghc-8.0.1-rc4: tyConRoles sees a TcTyCon

[GHC]

#12083: ghc-8.0.1-rc4: tyConRoles sees a TcTyCon
-------------------------------------+-------------------------------------
        Reporter:  _deepfire         |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1-rc4
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:  Yes.
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by mniip):

 I just hit what I think is an instance of this bug, but in a completely
 different setup. So here's another testcase I guess:

 {{{
 {-# LANGUAGE GADTs #-}

 module Bug where

 class Class a where
     test :: a -> (Eq a => r) -> r

 data P a b where
     Con :: (Class a, a ~ b) => P a b
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12083#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler