[GHC] #11449: Treat '_' consistently in type declarations

[GHC]

#11449: Treat '_' consistently in type declarations
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        Reporter:  simonpj           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      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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Comment (by simonpj):

 I meant `instance` sorry. I've fixed the ticket description.  Remember the
 description describes current behaviour.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11449#comment:5>
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