[GHC] #5211: Missing warning about redundant import for a class instance

[GHC]

#5211: Missing warning about redundant import for a class instance
---------------------------------------+------------------------------------
  Reporter:  Lemming                   |          Owner:                  
      Type:  bug                       |         Status:  closed          
  Priority:  normal                    |      Milestone:                  
 Component:  Compiler                  |        Version:  6.12.3          
Resolution:  fixed                     |       Keywords:                  
  Testcase:  rename/should_fail/T5211  |      Blockedby:                  
Difficulty:                            |             Os:  Unknown/Multiple
  Blocking:                            |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown              |  
---------------------------------------+------------------------------------
Changes (by simonpj):

  * status:  new => closed
  * testcase:  => rename/should_fail/T5211
  * resolution:  => fixed


Comment:

 Excellent point thank you!  Fixed by
 {{{
 commit 6f60f1f541cafdb3bfdd71d48eb9dd7f0a708bda
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Sat Jun 11 14:19:44 2011 +0100

     Fix tracking of what RdrNames are used (fixes Trac #5211)

     The issue here was: what import declaration brings into
     scope the 'op here

        import qualified Foo( op )
        import Bar( C(op) )
        instance C Int where
          op = ...

     Well, the import of Bar, obviously.  But what if the
     import Bar had been
        import Bar( C )
     Then the instance is still supposed to work, getting
     op from the Foo.op imported from Foo.  (I'm assuming its
     the same op, of course.)

 >---------------------------------------------------------------

  compiler/basicTypes/RdrName.lhs |    2 +-
  compiler/ghci/Debugger.hs       |    1 -
  compiler/rename/RnEnv.lhs       |   35
 ++++++++++++++++++++++++++---------
  3 files changed, 27 insertions(+), 11 deletions(-)
 }}}
 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5211#comment:1>
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