[GHC] #13754: ghc-8.0.2+ rejects more instance declarations

[GHC]

#13754: ghc-8.0.2+ rejects more instance declarations
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        Reporter:  zilinc            |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:  invalid           |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 > why it's not rejected by earlier (<8.0.2) versions of GHC

 I'm not certain, but I think it's because they had a slightly different
 implementation of instance declarations that had a fragile special case
 that happened to work.  But it's better now; more robust.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13754#comment:6>
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