[GHC] #7085: Report unused pattern bindings

[GHC]

#7085: Report unused pattern bindings
---------------------------------+------------------------------------------
    Reporter:  simonpj           |       Owner:                  
        Type:  feature request   |      Status:  new             
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.4.2           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by simonpj):

 I agree.  I've added extra behaviour to `-fwarn-unused-binds` so that it
 reports
  * Unused binders (as now), such as
 {{{
   let f x = x in 4  -- Binding for f is unused
 }}}
  * Unused pattern bindings (new), such as that above.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7085#comment:1>
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