[GHC] #10181: Lint check: arity invariant

[GHC]

#10181: Lint check: arity invariant
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        Reporter:  nomeata           |                   Owner:  nomeata
            Type:  task              |                  Status:  infoneeded
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.11
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by simonpj):

 This looks like a bug in the SOURCE-import mechanism to me.

 I think the same bug happens here:
 {{{
 bash$ ghc -c T8743.hs-boot
 bash$ ghc -c T8743.hs
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.8.2 for x86_64-unknown-linux):
         tcIfaceGlobal (local): not found:
     main:T8743.$fxToRowMaybe{v r2J}
     [(r2L, Class ‘main:T8743.ToRow{tc r2L}’),
      (r2M, Data constructor ‘main:T8743.D:ToRow{d r2M}’),
      (r2P, Identifier ‘main:T8743.D:ToRow{v r2P}’),
      (roB, Identifier ‘main:T8743.toRow{v roB}’),
      (rqT, Coercion axiom ‘main:T8743.NTCo:ToRow{tc rqT}’)]
 }}}
 Bother.  Well I suppose it would be good to open a separate ticket about
 that.  But I'll stick to my guns about `idArity <= typeArity` for now.
 See `Note [exprArity invariant]` in `CoreArity`.

 Did you find any other cases?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10181#comment:2>
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