[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:
            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 gershomb):

 I think Ed's comments on the two proposed plans of action are exactly
 right.

 Note that two things by the way are intersecting here: 1) GHC adding new
 warnings in general, which is largely unrelated to the 3-release policy
 but should be generally managed with some degree of rollout and 2) The
 presence of warnings at all such as redundant superclasses, which by their
 very nature warn against code that is necessary and desirable in migration
 paths. So lots of the details here don't apply to most warnings added --
 they apply to this particular one, and adding features so that it and
 similar warnings can more easily not stand in the way of library
 evolution, in general.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11370#comment:12>
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