[GHC] #4959: Warning about variables with leading underscore that are used anyway

[GHC]

#4959: Warning about variables with leading underscore that are used anyway
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    Reporter:  Lemming           |       Owner:                                    
        Type:  feature request   |      Status:  new                               
    Priority:  normal            |   Component:  Compiler (Parser)                 
     Version:  7.0.1             |    Keywords:  warning unused underscore variable
    Testcase:                    |   Blockedby:                                    
          Os:  Unknown/Multiple  |    Blocking:                                    
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown                      
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 I use -Wall all the time, which includes -fwarn-unused-binds and -fwarn-
 unused-matches that warn about variable bindings that are not used. It
 already spotted lots of mistakes for me. You can suppress the warning by
 prepending an underscore '_' to a variable name. However, I have recently
 seen code, where variable names with leading underscores are regularly
 used, where other programmers might have chosen trailing underscores or
 primes. I suspect that the programmer was not aware, that he disabled
 warnings about unused bindings this way. Thus I like to have a warning
 about underscored variables that are used in the sense of the definition
 given for -fwarn-unused-binds in
 http://www.haskell.org/ghc/docs/latest/html/users_guide/options-
 sanity.html.
 We still have to decide whether this warning should be part of -Wall or
 -fwarn-unused-binds or whether there should be a separate option like
 -fwarn-used-underscored-binds.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4959>
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