[GHC] #11813: Template Haskell's Exact names don't shadow correctly

[GHC]

#11813: Template Haskell's Exact names don't shadow correctly
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           Reporter:  goldfire       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Template       |           Version:  8.1
  Haskell                            |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Having two `Exact` names shadow one another confuses the renamer. In
 particular, if an `Exact` name is used twice in kind annotations of a type
 declaration, the `hsq_implicit` field of the `HsQTyVars` gets a duplicate.
 I've been unable to cause harm with this, but it's definitely wrong as is.

 Fix en route.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11813>
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