[GHC] #8132: Warning for Typeable instances misplaced

[GHC]

#8132: Warning for Typeable instances misplaced
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        Reporter:  scottgw                       |            Owner:
            Type:  bug                           |  dreixel
        Priority:  normal                        |           Status:  new
       Component:  Compiler                      |        Milestone:
      Resolution:                                |          Version:  7.7
Operating System:  Unknown/Multiple              |         Keywords:
 Type of failure:  Incorrect warning at          |     Architecture:
  compile-time                                   |  Unknown/Multiple
       Test Case:                                |       Difficulty:
        Blocking:                                |  Unknown
                                                 |       Blocked By:
                                                 |  Related Tickets:
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Comment (by scottgw):

 The disadvantage of amending the existing error is that it separates cause
 of the error from its from it symptom, and also doesn't pinpoint the cause
 reliably (You didn't write an instance! Or maybe you did and I ignored
 it!).

 The disadvantage of making a new error for this case is that clients who
 don't need the instance won't be able to compile until the package is
 fixed.

 I'm not sure what should constitute an error, but if GHC is just throwing
 these instances away because they are not allowed, then perhaps it makes
 sense to just disallow them.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8132#comment:2>
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