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

[GHC]

#10180: Lint check: Empty alternatives imply bottoming scrutinee
-------------------------------------+-------------------------------------
        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:
-------------------------------------+-------------------------------------
Changes (by nomeata):

 * status:  new => infoneeded


Comment:

 Sure enough, it trips over this
 {{{
 *** Core Lint errors : in result of Simplifier ***
 libraries/base/Data/Void.hs:66:8: Warning:
     [in body of lambda with binder a_a2y6 :: Void]
     No alternatives for a case scrutinee not known to diverge for sure:
 a_a2y6
 }}}

 Simon, what would you prefer: Should `exprIsBottom e` hold for all `e`
 where the type is a data type with no constructors, or should the lint
 check take that into account?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10180#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler