[GHC] #12007: Pattern families regression

[GHC]

#12007: Pattern families regression
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        Reporter:  MikeIzbicki       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mpickering):

 Sorry I was unclear in my last comment. The examples form the comment
 triggered the same kind of error in older builds but are now fixed. I can
 still reproduce the error you report but only when loading the file into
 ghci. I'm suggesting that whatever check is used to reject the now fixed
 examples should also reject the internally generated matching function
 which causes this panic.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12007#comment:6>
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