[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:  merge
        Priority:  normal            |            Milestone:  7.10.4
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by lehins):

 It's good to hear that it is fixed. It would be nice to know what is the
 actual cause and a reliable way to avoid this bug with ghc-8.0.2 and
 older, so anybody who stumbles upon it has a workaround. It feels like it
 has something to do with class constraints and inlining, but what exactly
 is still a mystery to me.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13429#comment:5>
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