Re: [GHC] #8506: misleading error message for duplicate type class instances

7 Nov 2013

      #8506: misleading error message for duplicate type class instances
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        Reporter:  carter                    |            Owner:
            Type:  bug                       |           Status:  closed
        Priority:  normal                    |        Milestone:
       Component:  Compiler (Type checker)   |          Version:  7.6.3
      Resolution:  fixed                     |         Keywords:
Operating System:  Unknown/Multiple          |     Architecture:
 Type of failure:  None/Unknown              |  Unknown/Multiple
       Test Case:  parser/should_fail/T8506  |       Difficulty:  Unknown
        Blocking:                            |       Blocked By:
                                             |  Related Tickets:
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Comment (by Simon Peyton Jones ):

 In [changeset:"384398b3eb2bc36a3e7b42a51495bd89398075b5/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="384398b3eb2bc36a3e7b42a51495bd89398075b5"
 Allow optional 'family' and 'instance' keywords in associated type
 instances

 This is to allow

    class C a where
       type family F a
       type instance F a = Bool

    instance C Int where
       type instance F Int = Char

 Plus minor improvements relating to Trac #8506
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8506#comment:9
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