[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"
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        Reporter:  antalsz           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |             Keywords:  TypeFamilies,
      Resolution:                    |  CustomTypeErrors
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I've confirmed that 2f9f1f86849ebc18af409c9b3fd809c9cd464021 (the fix for
 #13487) fixes this program as well. Curiously, #13487 was marked as merge,
 but hasn't made it into 8.2 for some reason. Can we do so?

 I'll prepare a regression test.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12104#comment:8>
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