[GHC] #10181: Lint check: arity invariant

[GHC]

#10181: Lint check: arity invariant
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        Reporter:  nomeata           |                Owner:
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      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:751
       Wiki Page:                    |
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Comment (by ezyang):

 It seems unlikely that bullet (2) is the way to go: `idArity` is
 ostensibly saying something about the Core program it points to. Which
 causes the invariant to be violated first: the simplifier or demand
 analysis? I think that's the one that should be responsible for fixing the
 invariant.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10181#comment:15>
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