[GHC] #11011: Add type-indexed type representations (`TypeRep a`)

[GHC]

#11011: Add type-indexed type representations (`TypeRep a`)
-------------------------------------+-------------------------------------
        Reporter:  bjmprice          |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by ekmett):

 Up until now we seem to have been focused on getting the `Typeable`
 internals "right" rather than compatible. Fortunately, the vast majority
 of users of `Typeable` limit themselves to `deriving` and to `cast`, so
 whatever you do to the internals affects very few users.

 If you like the `TypeRep t` and `TypeRepX` convention, then I'd say go for
 it.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11011#comment:23>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler