[GHC] #9429: Alternative to type family Any

[GHC]

#9429: Alternative to type family Any
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              Reporter:  mboes       |            Owner:
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.9
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:  9097, 9380
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 I'm a bit lost in this thread.  As Richard says (comment:17),
  * `Any` is still a valid type that can inhabit any kind
  * but you can't pattern-match on it in an instance declaration
 There are good reasons for this design.  One that has not been mentioned
 so far is #7259: eta expansion of products.  Admittedly we don't have this
 now, but in some sense we should have, and I'd be reluctant to move to a
 design that precluded it.

 If there is still a lack, could someone articulate just what it is,
 preferably explicitly (articulating problem, solution) rather than by
 saying that `rank1dyanamic` doesn't work.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9429#comment:19>
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