[GHC] #10189: explicit promotions of prefix data constructors can't be parsed naturally

[GHC]

#10189: explicit promotions of prefix data constructors can't be parsed naturally
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        Reporter:  Kinokkory         |                   Owner:  Kinokkory
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.8.4
  (Parser)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |                Blocking:
      Blocked By:                    |  Differential Revisions:
 Related Tickets:  #10188            |
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Comment (by goldfire):

 If we go with comment:5, that doesn't provide much of a migration path.
 The change would affect anyone using symbolic constructors prefix ''and''
 anyone using alphanumeric constructors infix.

 I agree that this affects a tiny segment of our users. Part of the reason
 I don't feel like we need to change this is that I'm foreseeing a future
 where `'` can scope over a bunch of constructors, like `'(Just (Succ Succ
 Zero))` and the `'` just signifies a namespace change.

 Call me ambivalent on this.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10189#comment:6>
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