[GHC] #11370: Redundant superclass warnings being included in -Wall destroys the "3 Release Policy"

[GHC]

#11370: Redundant superclass warnings being included in -Wall destroys the "3
Release Policy"
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        Reporter:  ekmett            |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  7.10.3
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11369, #11429    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 One open question here is how this should interact with #10632, which
 requests warnings for unused implicit parameters. This was addressed with
 `-Wredundant-constraints`, which we are now disabling by default. Is it
 reasonable to expect users to enable `-Wredundant-constraints` to be
 warned of unused implicit parameters? Implicit parameters "feel" a lot
 more like arguments than constraints.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11370#comment:19>
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