[GHC] #9242: Implement {-# OVERLAPPABLE #-} and {-# INCOHERENT #-} pragmas

[GHC]

#9242: Implement {-# OVERLAPPABLE #-} and {-# INCOHERENT #-} pragmas
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              Reporter:  simonpj     |            Owner:  diatchki
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.8.2
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by dterei):

 I noticed Andreas Abel on the mailing list objected to removing `OVERLAPS`
 but otherwise felt people were silent on the issue. We don't want to just
 make a chance in `-XSafe` as ideally `-XSafe` and GHC Haskell are as close
 as possible, otherwise the long term viability of Safe Haskell isn't good.

 I'll see what support I can rally or alternatives come up.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9242#comment:33>
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