[GHC] #14728: Is (GeneralizedNewtypeDeriving + associated type classes) completely bogus?

[GHC]

#14728: Is (GeneralizedNewtypeDeriving + associated type classes) completely bogus?
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.2
  checker)                           |             Keywords:  deriving,
      Resolution:                    |  TypeFamilies
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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Comment (by goldfire):

 Good about generating Core for type instances. Then this is all doable
 today.

 `axIdentity` is the newtype axiom that comes into being when a user
 declares a newtype. It can be accessed by `coerce`, but is mostly internal
 magic. Specifically, if you write

 {{{
 newtype N a b c = MkN (some_type)
 }}}

 then we get

 {{{
 axN :: N a b c ~R some_type
 }}}

 as an axiom (type `CoAxiom` in GHC).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14728#comment:6>
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