[GHC] #12104: Type families, `TypeError`, and `-fdefer-type-errors` cause "opt_univ fell into a hole"

[GHC]

#12104: Type families, `TypeError`, and `-fdefer-type-errors` cause "opt_univ fell
into a hole"
-------------------------------------+-------------------------------------
        Reporter:  antalsz           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  TypeFamilies,
                                     |  CustomTypeErrors
Operating System:  MacOS X           |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by antalsz):

 * Attachment "type-families-TypeError-defer-type-errors-opt_univ-bug.hs"
 added.

 The minimal example contained in the text of the ticket

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12104>
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