[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:  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):

 For what it's worth, I figured out a reliable way to avoid the bug, namely
 adding an extra constraint `Array X e`.

 So changing the type signature of `correlate` to:

 `correlate :: (Array X e, Array cs e) => Image X e -> Image cs e -> Image
 cs e`

 can be used as a trick for working around the bug.

 Not sure if it is relevant, but maybe it will help in narrowing down a
 possible cause.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13429#comment:10>
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