[GHC] #9778: Namespace collision detection for promoted types

[GHC]

#9778: Namespace collision detection for promoted types
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              Reporter:  crockeea    |            Owner:
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.8.3
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by crockeea):

 It seems there are a couple of options:

   1. Solve this problem by making DataKinds always promote to `'S`, and
 never to `S`. I'm sure this was long-debated when DataKinds was
 introduced, and is therefore unlikely to happen.
   2. Add a very mild message anytime there is a type error about a type
 that shares a name with a promoted constructor, something like "Be aware
 that S could refer to the constructor promoted from blah"

 Either one is an improvement over the current black-holing of promoted
 types when a non-promoted type is in scope.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9778#comment:5>
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