[GHC] #12772: (type f1 ~> f2 = forall a. f1 a -> f2 a) to core libraries

[GHC]

#12772: (type f1 ~> f2 = forall a. f1 a -> f2 a) to core libraries
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        Reporter:  Iceland_jack      |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Build System      |              Version:  8.0.1
      Resolution:                    |             Keywords:
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 RyanGlScott):

 > Is this something that belongs to core libraries

 I don't know. Which "core libraries" are you referring to? `base`,
 presumably? If so, this proposal should probably be advertised through the
 [https://mail.haskell.org/mailman/listinfo/libraries libraries mailing
 list] to gain a wider audience.

 But I can offer my two cents here: I really don't think this something
 that `base` urgently needs. For one thing, this is pretty non-standard
 Haskell in the sense that (1) it requires a GHC extension to use, and (2)
 it relies on a peculiarity of the GHC parser in order to even be
 //parsed// correctly (i.e., the definition of `(~>)` won't even parse
 prior to GHC 7.6).

 Portability issues aside, you mentioned the other issue looming over this
 proposal—its usefulness. It certainly straddles the Fairbairn threshold
 quite closely, and moreover, I'm unconvinced that adding this to `base`
 will be of much use at all considering the ease with which you can
 redefine `(~>)` in your own projects.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12772#comment:6>
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