[GHC] #4478: Exporting the same entity twice should not be a warning

[GHC]

#4478: Exporting the same entity twice should not be a warning
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    Reporter:  kosmikus          |       Owner:                                   
        Type:  bug               |      Status:  new                              
    Priority:  normal            |   Component:  Compiler                         
     Version:  6.12.3            |    Keywords:                                   
    Testcase:                    |   Blockedby:                                   
          Os:  Unknown/Multiple  |    Blocking:                                   
Architecture:  Unknown/Multiple  |     Failure:  Incorrect warning at compile-time
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Comment(by isaacdupree):

 Probably iff the name isn't mentioned explicitly at all, only through
 module re-exports, then there shouldn't be a warning here.

 If you said (..., module Data.List, module Data.List) then there could
 still sensibly be a warning for saying you're exporting the same
 ''module'' twice (which exists: "{{{Warning: Duplicate `Module Data.List'
 in export list}}}" and which already skips the individual duplicate
 warnings in this case).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4478#comment:2>
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