[GHC] #14170: 8.2.1 regression: GHC fails to simplify `natVal`

[GHC]

#14170: 8.2.1 regression: GHC fails to simplify `natVal`
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        Reporter:  vagarenko         |                Owner:  Bodigrim
            Type:  bug               |               Status:  patch
        Priority:  high              |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4212
       Wiki Page:                    |
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Comment (by hsyl20):

 I've just rebased D4212 on master. It should be ready to land.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14170#comment:17>
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