[GHC] #11390: GHC does not warn about redundant patterns

[GHC]

#11390: GHC does not warn about redundant patterns
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:  warnings,
                                     |  PatternMatchWarnings
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 I agree with George (gkaracha). `sillyId x = x` can't be called on a
 value, but Haskell isn't call-by-value. I will use `Void` instead of `F1
 Char`, because the type family bit isn't the interesting part here.

 {{{
 silly1 :: Void -> Void
 silly1 x = x

 silly2 :: Void -> Void
 silly2 x = error "urk"
 }}}

 `silly1 undefined` and `silly2 undefined` have different runtime behavior;
 the pattern is not redundant.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11390#comment:12>
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