Re: [GHC] #15305: Erroneous "non-exhaustive pattern match" using nested GADT with strictness annotation

24 Jul 2018

      #15305: Erroneous "non-exhaustive pattern match" using nested GADT with strictness
annotation
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        Reporter:  jkoppel           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.4.3
  checker)                           |             Keywords:
      Resolution:                    |  PatternMatchWarnings
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 To be clear, this is another occurrence of this phenomenon, right?

 {{{#!hs
 {-# LANGUAGE EmptyCase #-}
 {-# OPTIONS_GHC -Wincomplete-patterns #-}
 module Bug where

 import Data.Void

 data Abyss = Abyss !Void

 stareIntoTheAbyss :: Abyss -> a
 stareIntoTheAbyss a = case a of {}
 }}}

 (In that GHC warns that `stareIntoTheAbyss` in non-exhaustive, even though
 it shouldn't?)

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15305#comment:6
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