[GHC] #10604: Make Generic1 kind polymorphic

[GHC]

#10604: Make Generic1 kind polymorphic
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        Reporter:  DerekElkins       |                   Owner:  ekmett
            Type:  feature request   |                  Status:  new
        Priority:  low               |               Milestone:
       Component:  Core Libraries    |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Old description:

> It looks to me that the Generic1 class (and the Rep1 associated type) can
> immediately be generalized to forall k. k -> *.  If k was instantiated to
> anything other than *, you wouldn't be able to make an instance for Par1,
> but then I don't think it would ever come up so that would be exactly the
> right behavior.  This allows, in particular, DataKinds to be used as a
> parameter to instances of Generic1.
>
> I don't know if this would affect deriving, but I wouldn't really expect
> it to.

New description:

 It looks to me that the `Generic1` class (and the `Rep1` associated type)
 can immediately be generalized to `forall k. k -> *`.  If `k` was
 instantiated to anything other than `*`, you wouldn't be able to make an
 instance for `Par1`, but then I don't think it would ever come up so that
 would be exactly the right behavior.  This allows, in particular,
 `DataKinds` to be used as a parameter to instances of `Generic1`.

 I don't know if this would affect deriving, but I wouldn't really expect
 it to.

--

Comment (by simonpj):

 Happily, Andres Loh has agreed to take a lead in `Generics` and
 `DeriveAnyClass`, but only later this summer.  Thanks Andres!

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10604#comment:1>
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