[GHC] #14391: Make the simplifier independent of the typechecker

[GHC]

#14391: Make the simplifier independent of the typechecker
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        Reporter:  nomeata           |                Owner:  monoidal
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4503,
       Wiki Page:                    |  Phab:D5135
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Comment (by nomeata):

 `CoreM` is used by plugins, so to find out if anyone uses it, you’d have
 to go through various plugins. (But because it is a type class instance,
 you cannot reliably tell if an occurence of `lookupThing` in a plugin is
 actually using this instance … so I guess you just have to try building
 them)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14391#comment:38>
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