[GHC] #12785: GHC panic, `tcTyVarDetails` is missing a case (was: GHC panic, TypeFamily in equality constraint)

[GHC]

#12785: GHC panic, `tcTyVarDetails` is missing a case
-------------------------------------+-------------------------------------
        Reporter:  heisenbug         |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:  yes
      Blocked By:                    |             Blocking:
 Related Tickets:  #12590            |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by heisenbug):

 * failure:  None/Unknown => Compile-time crash or panic


--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12785#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler