[GHC] #13415: Instance declarations don't recognize named wildcards

[GHC]

#13415: Instance declarations don't recognize named wildcards
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13324            |  Differential Rev(s):  Phab:D3332
       Wiki Page:                    |
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Comment (by simonpj):

 I still don't know what you are trying to achieve.  The error message
 looks spot on to me, and is the same whether you write `x`, `x_`, `_x` or
 `xx`, just as it is in any other type that does not admit wildcards.
 What error message do you actually want?  What about the other uses of
 `LHsSigType`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13415#comment:6>
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