[GHC] #1316: add warning for local type signatures that use the same type variable names as outer type signatures

[GHC]

#1316: add warning for local type signatures that use the same type variable names
as outer type signatures
---------------------------------+------------------------------------------
    Reporter:  Isaac Dupree      |       Owner:  simonpj         
        Type:  feature request   |      Status:  new             
    Priority:  normal            |   Milestone:  _|_             
   Component:  Compiler          |     Version:  6.6.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by morabbin):

 To summarize, the proposal is that code like the o.p.'s should produce a
 warning when `-XScopedTypeVariables` is not in effect.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1316#comment:9>
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