[GHC] #4139: Spurious non-exhaustive pattern match warnings are given using GADTs

[GHC]

#4139: Spurious non-exhaustive pattern match warnings are given using GADTs
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  Reporter:  blarsen                            |          Owner:                                   
      Type:  bug                                |         Status:  new                              
  Priority:  normal                             |      Milestone:  7.0.1                            
 Component:  Compiler                           |        Version:  7.4.1                            
Resolution:                                     |       Keywords:  GADTs, warnings, pattern matching
        Os:  Unknown/Multiple                   |   Architecture:  Unknown/Multiple                 
   Failure:  Incorrect warning at compile-time  |     Difficulty:                                   
  Testcase:                                     |      Blockedby:                                   
  Blocking:                                     |        Related:                                   
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Changes (by goldfire):

  * status:  closed => new
 * cc: eir@… (added)
  * failure:  None/Unknown => Incorrect warning at compile-time
  * version:  6.12.3 => 7.4.1
  * owner:  simonpj =>
  * resolution:  invalid =>


Comment:

 I have a case with the same bug description as above, but when I include
 the pattern suggested by the warning statement, I get a compiler error
 indicating unreachable code. I have attached my code.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4139#comment:4>
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