[GHC] #13429: Optimizer produces Core with an infinite <<loop>>

[GHC]

#13429: Optimizer produces Core with an infinite <<loop>>
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        Reporter:  lehins            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  7.10.4
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dfeuer):

 Simon, I can't speak for absolute HEAD, but I tried it with a very recent
 build and the bug happens there. I tried modifying the code to use type
 families and equality constraints to eliminate `FunctionalDependencies`,
 `FlexibleContexts`, and `UndecidableInstances`, but the same bug shows up.
 I've not yet been able to make the bug happen using single-parameter type
 classes, but that certainly doesn't mean it's impossible.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13429#comment:18>
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