[GHC] #13221: OccurAnal fails to rediscover join points

[GHC]

#13221: OccurAnal fails to rediscover join points
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           Reporter:  lukemaurer     |             Owner:  lukemaurer
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           Keywords:  JoinPoints     |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Not clear why the warning from `OccurAnal` about rediscovering join points
 is ever firing. There's one circumstance I can think of, namely the
 special typing rule allowing jumps from β-redexes, but the warning fires
 repeatedly and β-redexes don't survive the simplifier.

 This isn't hard evidence of something wrong, but it indicates the
 occurrence analyzer may be missing something.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13221>
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