[GHC] #9858: Typeable instances should be kind-aware

[GHC]

#9858: Typeable instances should be kind-aware
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        Reporter:  dreixel           |                   Owner:
            Type:  bug               |                  Status:  merge
        Priority:  highest           |               Milestone:  7.10.2
       Component:  Compiler          |                 Version:  7.9
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |  typecheck/should_fail/T9858a,
                                     |  should_run/T9858b
                                     |                Blocking:
                                     |  Differential Revisions:  Phab:D652
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Comment (by oerjan):

 Looking at
 [https://git.haskell.org/ghc.git/commitdiff/d8d541d85defcf3bbbddaeee8cfac70b74f47ffc
 the fix], I suspect it still does not disallow constructing `Typeable (Eq
 Int => Int)` by roundabout means - the test seems to be only for the fully
 applied form, not the lone `=>` constructor. However, with all the tuple
 constructors properly disambiguated, I don't think there's an exploit any
 more.

 I just realized my proof above doesn't handle kinds of `->` variants like
 `* -> # -> *`. But I'm not aware of any way to create an ambiguous
 `TypeRep` of possible kind `#`, so it should hopefully be fine.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9858#comment:97>
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