[GHC] #8516: Add (->) representation and the Invariant class to GHC.Generics

[GHC]

#8516: Add (->) representation and the Invariant class to GHC.Generics
-------------------------------------+-------------------------------------
        Reporter:  nfrisby           |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  low               |            Milestone:
       Component:  Compiler (Type    |              Version:  7.7
  checker)                           |
      Resolution:                    |             Keywords:  Generics
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 RyanGlScott):

 And as it turns out, goldfire has a separate ticket (#8177) for the
 proposed idea of being able to give explicit role signatures to type
 families, which might make the potential regression in
 [https://ghc.haskell.org/trac/ghc/ticket/8516#comment:7 this comment] not
 an actual regression. See my comment
 [https://ghc.haskell.org/trac/ghc/ticket/8177#comment:31 here].

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8516#comment:11>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler