[GHC] #8363: Order matters for unused import warnings when reexporting identifiers

[GHC]

#8363: Order matters for unused import warnings when reexporting identifiers
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        Reporter:  bergmark          |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by simonpj):

 Yes, you're right.  In general it's a hard problem to find the minimal set
 of imports that are required.  (It's a kind of set-covering problem.)  GHC
 uses a cheap and cheerful heuristic that usually does reasonably well.

 The code is very localised, in `RnNames.warnUnusedImportDecls`.  If anyone
 can do better, go for it!

 Simon

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8363#comment:1>
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