[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):

 > will get the immediate benefit of having better error messages

 Why will the error messages get better? Can you give an example?  Is that
 an argument for putting wildcards everywhere?  Why couldn't we just
 improve the error messages for `LHsSigType`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13415#comment:8>
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