[GHC] #8813: further support deriving instances Typeable1, Typeable2, etc

[GHC]

#8813: further support deriving instances Typeable1, Typeable2, etc
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        Reporter:  maeder                     |            Owner:  dreixel
            Type:  task                       |           Status:  merge
        Priority:  normal                     |        Milestone:
       Component:  Compiler                   |          Version:
      Resolution:                             |  7.8.1-rc1
Operating System:  Unknown/Multiple           |         Keywords:
 Type of failure:  GHC rejects valid program  |     Architecture:
       Test Case:                             |  Unknown/Multiple
        Blocking:                             |       Difficulty:  Unknown
                                              |       Blocked By:
                                              |  Related Tickets:
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Changes (by dreixel):

 * status:  new => merge


Comment:

 Replying to [comment:15 simonpj]:
 > Pedro said "I couldn't find an acceptable solution. But, as I said
 before, I would very much welcome a better solution."  Reid suggested one,
 perhaps one that Pedro thought of and discarded, perhaps not.  It has the
 advantage that it might be a simple change to `Data.Typeable` making
 (deprecated) exports of `Typeable1`, `Typeable2` etc.
 >
 > Pedro: can you think of any problems with this?  Thanks Reid.

 No, I hadn't thought of this before, and no, I don't see any problems with
 it. As has been pointed out already, it won't work for all old code. But
 it might still make some more code work, and I don't see a problem with
 including it. So I submitted a patch to base adding those. In particular,
 the original problem code described in this ticket should now compile
 (along with a deprecation warning).

 I've also updated the wiki page at
 https://ghc.haskell.org/trac/ghc/wiki/GhcKinds/PolyTypeable to refer to
 7.8 as the present, not the future, and I've added a section on how to
 make your code compile again. I've also added a link to this wiki page
 from the Data.Typeable haddock.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8813#comment:28>
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