[GHC] #16173: Move `Data.Profunctor` from `profunctors` package to `base`

[GHC]

#16173: Move `Data.Profunctor` from `profunctors` package to `base`
-------------------------------------+-------------------------------------
           Reporter:  chshersh       |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Core           |           Version:  8.6.3
  Libraries                          |
           Keywords:  base,          |  Operating System:  Unknown/Multiple
  profunctor, QuantifiedConstraints  |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  #14767
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 `Contravariant` was added in GHC 8.6.

 * https://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Functor-
 Contravariant.html

 `Profunctor` also looks like fundamental abstraction to be worth
 considering adding to `base`.

 Having both `Profunctor` and `Choice` typeclasses in the `base` library
 will also allow to write `microprism` package similar to `microlens`.
 Prisms often turns to be very useful since they allow to work nicely with
 sum types.

 {{{#!hs
 type Prism s t a b = forall p f. (Choice p, Applicative f) => p a (f b) ->
 p s (f t)
 }}}

 Additional context for this ticket from Reddit:

 *
 https://www.reddit.com/r/haskell/comments/8v53cb/announce_ghc_861alpha1_available/e1o1giy/

 It was proposed on Reddit to use `QuantifiedConstraints` for `Profunctor`.
 I'm not quite fluent with `QuantifiedConstraints`, but I think this may
 looks like this (mostly copy-pasting code from `profunctors` package):

 {{{#!hs
 {-# LANGUAGE QuantifiedConstraints #-}

 class (forall a . Functor (p a)) => Profunctor p where
   {-# MINIMAL dimap | (lmap, rmap) #-}

   dimap :: (a -> b) -> (c -> d) -> p b c -> p a d
   dimap f g = lmap f . rmap g

   lmap :: (a -> b) -> p b c -> p a c
   lmap f = dimap f id

   rmap :: (b -> c) -> p a b -> p a c
   rmap = dimap id

 instance Profunctor (->) where
   dimap ab cd bc = cd . bc . ab
   lmap = flip (.)
   rmap = (.)
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16173>
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