[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):

 Ok, added it to the linter for now; whether `exprIsBottom` should be
 extended is a different question.

 Next linter error when compiling GHC:

 It complains about this code:
 {{{
 *** Core Lint errors : in result of Simplifier ***
 <no location info>: Warning:
     In a case alternative: (False)
     No alternatives for a case scrutinee not known to diverge for sure: \
 (@ a_agBy) ->
 lvl_smAM @ a_agBy ds3_alsA
 [...]
                                       case \ (@ a_agBy) -> lvl_smAM @
 a_agBy ds3_alsA
                                       of _ [Occ=Dead] {
 }}}

 So there is a lambda under the case, but it is a type lambda. Bogus or
 not?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10180#comment:2>
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