[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"
-------------------------------------+-------------------------------------
        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:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11369, #11429    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by simonmar):

 * owner:   => bgamari


Comment:

 The plan is:
 * `-Wall` will include `-Wredundant-constraints`
 * If at some point we have a compat warning that requires the addition of
 a redundant constraint to suppress it, then when this warning is enabled
 at the same time as `-Wredundant-constraints`, we will arrange to not emit
 a redundant constraint warning for constraints that are required to
 suppress the compatibility warning.

 Please let us know if this will cause a problem.  @bgamari is going to
 action the first change.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11370#comment:32>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler