[GHC] #13429: Optimizer produces Core with an infinite <<loop>>

[GHC]

#13429: Optimizer produces Core with an infinite <<loop>>
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        Reporter:  lehins            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  7.10.4
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Alberto Valverde [https://mail.haskell.org/pipermail/ghc-
 devs/2017-May/014222.html discovered] another occurrence of this bug: the
 `fingertree-0.1.1.0`
 [http://hackage.haskell.org/package/fingertree-0.1.1.0 test suite]:

 {{{
 $ ~/Software/ghc-8.0.2/bin/ghc -O -fforce-recomp FingerTreeTestMain.hs
 [1 of 2] Compiling FingerTree       ( FingerTree.hs, FingerTree.o )
 [2 of 2] Compiling Main             ( FingerTreeTestMain.hs,
 FingerTreeTestMain.o )
 Linking FingerTreeTestMain ...

 $ ./FingerTreeTestMain
 True

 $ ~/Software/ghc-8.2.0.20170507/bin/ghc -O -fforce-recomp
 FingerTreeTestMain.hs
 [1 of 2] Compiling FingerTree       ( FingerTree.hs, FingerTree.o )
 [2 of 2] Compiling Main             ( FingerTreeTestMain.hs,
 FingerTreeTestMain.o )
 Linking FingerTreeTestMain ...

 $ ./FingerTreeTestMain
 FingerTreeTestMain: <<loop>>
 }}}

 In case it's useful, I'll attach a minimized version of the test suite.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13429#comment:16>
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