[GHC] #13470: Pattern synonyms bind variables out of scope

[GHC]

#13470: Pattern synonyms bind variables out of scope
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        Reporter:  Iceland_jack      |                Owner:  mpickering
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
                                     |  PatternSynonyms
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3377
       Wiki Page:                    |
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Comment (by Matthew Pickering <matthewtpickering@…>):

 In [changeset:"d819e416a2a537b78b2698dfe753aa68dfb8b837/ghc" d819e41/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="d819e416a2a537b78b2698dfe753aa68dfb8b837"
 Only use locally bound variables in pattern synonym declarations

 Summary:
 We were using the unconstrainted `lookupOccRn` function which looked up
 any variable in scope. Instead we only want to consider variables brought
 into
 scope by renaming the pattern on the RHS.

 A few more changes to make reporting of unbound names suggest the correct
 things.

 Fixes #13470

 Reviewers: simonpj, austin, bgamari

 Reviewed By: simonpj

 Subscribers: rwbarton, thomie

 Differential Revision: https://phabricator.haskell.org/D3377
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13470#comment:7>
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