[GHC] #9123: Need for higher kinded roles

[GHC]

#9123: Need for higher kinded roles
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  7.8.2
  checker)                           |             Keywords:  Roles,
      Resolution:                    |  QuantifiedConstraints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  quantified-
                                     |  constraints/T9123{,a}
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by goldfire):

 * owner:  goldfire => (none)
 * status:  closed => new
 * resolution:  fixed =>


Comment:

 We cannot yet accept the program in the original post, due to (at least)
 #15290. I also think that, in the case of inferring the constraints in a
 `deriving` clause, we ''should'' sometimes infer a quantified constraint.
 I'd like to keep this ticket open until we can safely put `join` into
 `Monad`.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9123#comment:58>
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