[GHC] #10218: GHC creates incorrect code which throws <<loop>>

[GHC]

#10218: GHC creates incorrect code which throws <<loop>>
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        Reporter:  yongqli           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:  yes
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by AlexET):

 I have managed to reproduce on windows 64-bit on GHC-7.10.1. I have shrunk
 the example down. It requires linear, vector and transformers. It needs to
 be complied with -O1 and -feager-blackholes.

 The redundant constraint in the context of the type of guessStates is
 required for the bug to trigger. Inlining calc_zs also  prevents the bug
 from triggering. Adding sharing between xs and ys in guessStates also
 prevents the bug. Changing the monad to the Identity monad prevents the
 bug. Removing the VectorSpace space class and just adding the constraints
 to LinAlg also prevents the bug.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10218#comment:2>
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