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

[GHC]

#11011: Add type-indexed type representations (`TypeRep a`)
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        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:                    |
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Changes (by simonpj):

 * cc: ekmett, core-libraries-committee@… (added)


Comment:

 It's clear that we'll continue to want bot a type-indexed and non-type-
 indexed representation.  The only question is whether they are called
  * `TypeRep t`: type indexed
  * `TypeRepX`: non-indexed
 or
  * `TypeRepT t` or `TTypeRep t`: type indexed
  * `TypeRep`: non-indexed

 The latter has the merit of being more backward compatible. The former is
 nicer to my mind.

 Adding Edward and the Core Libraries Committee.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11011#comment:21>
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