[GHC] #12556: `stimes` adds extra power to Semigroup

[GHC]

#12556: `stimes` adds extra power to Semigroup
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        Reporter:  Iceland_jack      |                Owner:
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  libraries/base    |              Version:  8.0.1
      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 rwbarton):

 It doesn't seem like a problem to me if a particular `Semigroup`'s
 `stimes` is more defined than the default definition would be, as long as
 that extension is reasonable, i.e., a monoid homomorphism. Even allowing
 negative arguments would be reasonable if the `Semigroup` happens to be a
 group.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12556#comment:3>
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