[GHC] #13401: GHCi gives conflicting information about visible type application

[GHC]

#13401: GHCi gives conflicting information about visible type application
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        Reporter:  crockeea          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.0.1
      Resolution:                    |             Keywords:
                                     |  TypeApplications
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11376, #11975    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by crockeea):

 The reason I feel that GHCi is giving me incorrect info is due to the
 existing documentation that I quoted above. Basically, my understanding is
 that if `foo :: forall {k} . k` then GHCi should throw an error if I try
 to write `foo @Int`, and if `foo :: forall k . k`, then GHCi should
 happily accept `foo @Int`.

 When I see `foo :: forall {k} . k`, but GHCi also lets me write `foo
 @Int`, I have no idea what it means by `{k}`. This seems like a
 contradiction. I get the impression from your comments that there's
 something more subtle going on here that I don't understand. If you think
 others might have the same misconception as me, I would encourage you to
 improve the existing docs as well.

 In regards to your suggestion, I think it would be good to put a blurb in
 the Visible Type Application section (9.18 by my count) as well, near the
 "detail" note that explains the curly braces.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13401#comment:7>
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