[GHC] #11806: GHC does not warn for mistakenly empty case

7 Apr 2016

      #11806: GHC does not warn for mistakenly empty case
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           Reporter:  dfeuer         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  GHC accepts
  Unknown/Multiple                   |  invalid program
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 {{{#!hs
 {-# LANGUAGE EmptyCase #-}
 {-# OPTIONS_GHC -Wall -fwarn-incomplete-uni-patterns #-}

 oops :: Int -> a
 oops x = case x of {}
 }}}

 Since `Int` is inhabited, I would expect a warning, but I get none. Since
 empty case is typically used in situations where programmers want GHC to
 see an absurdity, this seems most unfortunate.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11806
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