[GHC] #12466: Typechecker regression: Inaccessible code in a type expected by the context

[GHC]

#12466: Typechecker regression: Inaccessible code in a type expected by the context
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        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Oh gosh -- I've clearly been very confused. The original example makes
 sense to me only with a generic-default signature, so I assumed there was
 one. I've been thus babbling nonsense. Sorry, all!

 I have no idea why including the method implementation works. I don't
 think it should.

 But I still say the original code should be rejected for the same reasons
 I've already articulated. If inaccessible code were to become a warning,
 then the way to fix the warning is not to write the instance.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12466#comment:14>
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