[GHC] #10180: Lint check: Empty alternatives imply bottoming scrutinee

[GHC]

#10180: Lint check: Empty alternatives imply bottoming scrutinee
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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 nomeata):

 I’ll be happy to pursue this course and see how far it will take us, but
 my gut feeling is that this will never be complete and even if GHC+the
 test suite go through, someone will be able to figure out how to make the
 linter fail erroneously.

 Making the check use `dataConCannotMatch` now, but it uses
 `Unify.typesCantMatch` which does not even look through newtypes (yet), so
 this will only get us so far...

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10180#comment:10>
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