[GHC] #11540: ghc accepts non-standard type without language extension

[GHC]

#11540: ghc accepts non-standard type without language extension
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        Reporter:  augustss          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.8.4
  (Parser)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 That being said, it was decided at some point that we should also allow
 `foralls` independently from `RankNTypes` with `ExplicitForAlls`. My
 initial thought was that `RankNTypes` would imply `NestedContexts`, just
 as it does `ExplicitForAlls`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11540#comment:3>
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