[GHC] #8185: Change role annotation syntax

[GHC]

#8185: Change role annotation syntax
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        Reporter:           |            Owner:  goldfire
  goldfire                  |           Status:  new
            Type:  feature  |        Milestone:  7.8.1
  request                   |          Version:  7.7
        Priority:  normal   |         Keywords:
       Component:           |     Architecture:  Unknown/Multiple
  Compiler                  |       Difficulty:  Moderate (less than a day)
      Resolution:           |       Blocked By:
Operating System:           |  Related Tickets:
  Unknown/Multiple          |
 Type of failure:           |
  None/Unknown              |
       Test Case:           |
        Blocking:           |
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Comment (by simonpj):

 I hate the idea of permanently messing up the language to secure backward
 compatibility.  Maybe we can split into two questions:
  * What "should" it look like?
  * How can we secure backward compat?

 For the latter we might argue that of these two:
 {{{
    {-# ROLES Map nominal representational #-}
 and
    #ifdef GHC >= 7.8
    roles Map nominal representational
    #endif
 }}}
 that the former is so much better than the latter that we should support
 pragma syntax.  (To me it's a bit moot, but I'll go with the flow.)  But
 it still smells wrong to me to ''only'' have pragma syntax.

 Simon

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8185#comment:10>
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