[GHC] #13521: Remove comments about API annotations

[GHC]

#13521: Remove comments about API annotations
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           Reporter:  mpickering     |             Owner:  (none)
               Type:  task           |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
  ApiAnnotations                     |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 There are lots of comments scattered around the code which look like

 {{{
          -- - 'ApiAnnotation.AnnKeywordId's : 'ApiAnnotation.AnnOpen',
          --                                   'ApiAnnotation.AnnClose',
          --                                   'ApiAnnotation.AnnComma',
          --                                   'ApiAnnotation.AnnType'

          -- For details on above see note [Api annotations] in
 ApiAnnotation
 }}}

 these are meant to tell you which annotations are associated with each
 syntax element.
 They were added in an heroic effort by alanz but are very hard to keep up
 to date and verify the correctness of.

 It would be much better if we had a programatic description of which
 annotations could be attached to which syntax elements and thankfully one
 already exists in `ghc-exactprint`. This library isn't in the source tree
 but I don't think this really matters, users can just depend on it if they
 want to use them.

 I think we should remove all these comments to clean up the source a bit
 and point users to `ghc-exactprint` from the `ApiAnnotations` page.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13521>
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