[GHC] #13064: Incorrect redudant imports warning

[GHC]

#13064: Incorrect redudant imports warning
-------------------------------------+-------------------------------------
        Reporter:  phadej            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  low               |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15393            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 To follow up on my proposed experiment (in comment:29), I built about 143
 commonly used Hackage libraries using the `wip/T13064` GHC branch. Of
 those 143, I noticed new warnings being emitted in 31 of them (~22%):

 {{{
 - adjunctions-4.4
 - aeson-1.4.0.0
 - ansi-wl-pprint-0.6.8.2
 - asn1-encoding-0.9.5
 - async-2.2.1
 - attoparsec-0.13.2.2
 - blaze-builder-0.4.1.0
 - cassava-0.5.1.0
 - conduit-1.3.0.3
 - cookie-0.4.4
 - foundation-0.0.21
 - Glob-0.9.2
 - haskell-src-exts-1.20.2
 - hspec-core-2.5.6
 - lens-4.17
 - math-functions-0.3.0.2
 - memory-0.14.16
 - microstache-1.0.1.1
 - mono-traversable-1.0.9.0
 - network-2.8.0.0
 - primitive-0.6.4.0
 - resourcet-1.2.1
 - scientific-0.3.6.2
 - tasty-1.1.0.3
 - th-orphans-0.13.6
 - unordered-containers-0.2.9.0
 - uuid-types-1.0.3
 - x509-1.7.4
 - x509-store-1.6.6
 - x509-system-1.6.6
 - yaml-0.10.1.1
 }}}

 I still advocate adopting this change, but it is worth noting that a non-
 trivial number of existing libraries will need to be updated in order to
 accommodate the new warnings.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13064#comment:36>
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