[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 simonpj):

 Thanks, that's helpful.  Does the `fingertree` example of the bug happen
 in HEAD?  (The other example does not.)   Are you sure it's the same bug?

 Just for info, I have investigated this a bit, and I know what's going on.
 The tricky bit is that we want to specialise dictionary functions (which
 arise from instance decls); but they produce dictionaries, and it's rather
 easy to mess up.

 I think I have a reasonably simple solution, but it's a solition I can't
 say is wrong, rather than one that obviously right.  So I've been
 ruminating, so far to little avail.

 Is it actually a show-stopper for anyone?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13429#comment:17>
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