[GHC] #9178: improve orphan instance warning

[GHC]

#9178: improve orphan instance warning
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       Reporter:  fphh              |             Owner:
           Type:  task              |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  Compiler          |           Version:  7.8.2
       Keywords:                    |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:                    |
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 The current warning

 `Warning: orphan instance: instance ClassName TypeName`

 could be improved by suggesting three solutions:

 (i) Move the instance declaration to the file, where the class has been
 declared
 (ii) Move the instance declaration to the file, where the Type has been
 declared
 (iii) Wrap the type with a newtype and declare the instance on the new
 type.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9178>
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