[GHC] #9515: Deprecate -XExplicitForAll

[GHC]

#9515: Deprecate -XExplicitForAll
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              Reporter:  dfeuer      |            Owner:
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.8.3
             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 dfeuer):

 This only affects code that does something a bit strange. In particular,
 it has to use a `forall` in an outer position (not for a higher-rank type
 or an eqxistential) and it reuse the same type variable without a new
 `forall`. I'd be happy to participate in a survey of Hackage code, but I'm
 not sure how to go about that—there are thousands of files on Hackage.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9515#comment:9>
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