[GHC] #15457: (~) and (!) are parsed inconsistently in types (plus documentation warts)

[GHC]

#15457: (~) and (!) are parsed inconsistently in types (plus documentation warts)
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
  (Parser)                           |
      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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Changes (by RyanGlScott):

 * status:  patch => new
 * differential:  Phab:D5023 =>


Comment:

 The approach in Phab:D5023 isn't quite up to snuff, since it leaves some
 scenarios where `!` isn't parsed in a precedence-aware fashion (see
 https://phabricator.haskell.org/D5023#139341). To handle that situation
 correctly, we'd need to implement something skin to the plan laid out in
 https://phabricator.haskell.org/D5023#139245.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15457#comment:2>
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