[GHC] #9575: -XAutoDeriveTypeable fails to generate instances

[GHC]

#9575: -XAutoDeriveTypeable fails to generate instances
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              Reporter:  hvr         |            Owner:  dreixel
                  Type:  bug         |           Status:  new
              Priority:  high        |        Milestone:  7.8.4
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by rwbarton):

 See ticket:8950#comment:3.

 I don't see what there is to gain by backporting a fix though, even if you
 could detect GHC 7.8.4, it's still more effort to do so than to just add
 `Typeable` to the deriving list. And it could break old code that uses
 `AutoDeriveTypeable`, by causing it to export more instances than it did
 under 7.8.3.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9575#comment:2>
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