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

[GHC]

#8813: further support deriving instances Typeable1, Typeable2, etc
----------------------------------------------+----------------------------
        Reporter:  maeder                     |            Owner:
            Type:  task                       |           Status:  new
        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:
----------------------------------------------+----------------------------

Comment (by rwbarton):

 Christian: actually that does work.

 That seems like a decent argument to include these type synonyms for
 backwards-compatibility purposes. (As kosmikus notes, they're still not
 100% backwards compatible. For example, `Typeable` still doesn't fix the
 kind of its argument, which could matter in a module with `PolyKinds`; and
 since `TypeableN` is now a type synonym it can't be the argument to
 another type constructor (with `ConstraintKinds`). But those are both
 fairly obscure cases.)

 I fully agree though that the type synonyms should be marked as
 deprecated. `TypeableN` is a hack that served its purpose; now we can
 express our programs better using orthogonal features (polykinded types
 and kind signatures).

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8813#comment:19>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler