[GHC] #11630: More precise LANGUAGE pragma when forall is used

[GHC]

#11630: More precise LANGUAGE pragma when forall is used
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           Reporter:  ezyang         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  low            |         Milestone:
          Component:  Compiler       |           Version:  8.1
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 In all cases when a user attempts to use the `forall` keyword, GHC
 suggests enabling `RankNTypes`. This seems suboptimal, since a more direct
 way to enable just the syntax is `ExplicitForAll`. So maybe we should just
 suggest that instead.

 In some cases, the user will immediately thereafter have to add
 `RankNTypes`, or `Rank2Types`, or `ExistentialQuantification`, etc. So it
 would be more user friendly to suggest the appropriate extension directly.
 I don't know how much harder this would be to do.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11630>
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