[GHC] #11822: Pattern match checker exceeded (2000000) iterations

[GHC]

#11822: Pattern match checker exceeded (2000000) iterations
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        Reporter:  j.waldmann        |                Owner:  gkaracha
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1-rc3
      Resolution:                    |             Keywords:
                                     |  PatternMatchWarnings
Operating System:  Unknown/Multiple  |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by NeilMitchell):

 There are some warnings that are on by default, and some that are only on
 with {{-Wall}}. Making this a warning that was not triggered by default
 but was by {{-Wall}} would give you what you want.

 As to my personal opinion, I want my code to compile without warnings. If
 you can give me a warning that I have an undesirable problem, and I can
 reasonably mitigate it, I'm happy. If you give me a vague sense of unease
 about limitations in your checker, and I can't do anything with it other
 than disable warnings, I'm sad. The warning above doesn't relate to
 whether there are inexhaustive patterns or not, it's all about whether
 your checker can prove that, which is a different thing.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11822#comment:10>
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