[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:
            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:                    |
-------------------------------------+-------------------------------------
Changes (by hvr):

 * related:  #11369 => #11369, #11429


Comment:

 Replying to [comment:7 ekmett]:
 > I think Herbert was leaning towards `-Weverything`.

 Indeed, because we have a precedent in `clang` which uses `-Weverything`
 for that very purpose (since `-Wall` is traditionally doesn't comprise
 *all* warnings for gcc/clang, which is probably also the origin from where
 GHC copied this tradition...)

 Replying to [comment:8 ekmett]:
 > Possibly with Gershom's suggestion from the mailing list of making
 unrecognized `-Wfoo` options emit a single warning about an unrecognized
 option rather than have the compiler emit an error and die.

 Filed as #11429 -- if we agree this is a sensible thing to do, I think we
 should try to get this done in time for GHC 8.0 to extend the compat-
 window as far back as possible, i.e. starting at GHC 8.0 for a `-Wno-
 unrecognised-warning-flags` (module bikeshed) support

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11370#comment:9>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler