[GHC] #12044: Remove sortWith in favor of sortOn

[GHC]

#12044: Remove sortWith in favor of sortOn
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        Reporter:  cblp              |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  libraries/base    |              Version:  7.10.3
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #2659             |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by thomie):

 * keywords:   => newcomer
 * related:  2659 => #2659


Comment:

 Sure. Do something like this:
 * add a `DEPRECATED` pragma to `sortWith`
 * add an entry in the base release notes (`libraries/base/changelog.md`)
 that `sortWith` is deprecated
 * replace use of `sortWith` in the compiler, libraries, and testsuite by
 `sortOn`
 * replace the implementation of `sortWith` by a call to `sortOn`
 (optional)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12044#comment:1>
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