[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            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 I’m not sure if the 3-release-policy should get in the way of useful
 compilier output, and `-Wall` is (rightfully) used by developers to ask
 the compiler to comment the code as much as sensibly possible.

 We could refine the policy to promise (or thrive) to deliver `-Wall -Wno-
 redundant-constraints` cleanliness, and similarly disable other warnings
 that get in the way of a nice backward-facing compatibility story.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11370#comment:2>
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