[GHC] #8539: Data.Complex shouldn't use default implementation of (**)

[GHC]

#8539: Data.Complex shouldn't use default implementation of (**)
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        Reporter:  jjaredsimpson     |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  low               |               Milestone:  7.12.1
       Component:  Prelude           |                 Version:  7.6.3
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by ekmett):

 Hacking up your patch to change the shadowing `x` and two shadowing `y`s
 should do it. e.g.

 {{{
 +      ((re:+im), y)
 +        | (isInfinite re || isInfinite im) -> case y of
 -      ((re:+im), y')
 -        | (isInfinite re || isInfinite im) -> case y' of

 -      (x, y)         ->  exp (log x * y)
 +      (x', y')         ->  exp (log x' * y')
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8539#comment:39>
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