Re: [GHC] #13625: GHC internal error: ‘Y’ is not in scope during type checking, but it passed the renamer

19 May 2017

      #13625: GHC internal error: ‘Y’ is not in scope during type checking, but it passed
the renamer
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        Reporter:  mpickering        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  TypeInType
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 Simon Peyton Jones ):

 In [changeset:"2501fb70691f80b9c48e5f9bdea3b897653f499a/ghc"
 2501fb70/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="2501fb70691f80b9c48e5f9bdea3b897653f499a"
 Fix scoping of data cons during kind checking

 Trac #13625 pointed out that in

    data X :: Y where Y :: X

 we need 'Y' to be in scope (as APromotionErr) when dealing with
 X's kind signature.  Previously we got a crash.

 This patch simplifies the code as well as making it work.
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13625#comment:2
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