[GHC] #11367: [Regression] Only one clause allowed in (explicitly bidirectional) pattern synonyms

[GHC]

#11367: [Regression] Only one clause allowed in (explicitly bidirectional) pattern
synonyms
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
                                     |  PatternSynonyms
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #393 #5791        |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"443bf04485f997be2e3a744102605645c54e9d61/ghc" 443bf04/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="443bf04485f997be2e3a744102605645c54e9d61"
 Allow pattern synonyms which have several clauses.

 But still disallow empty pattern synonym builder declarations. Handling
 this incorrectly was the cause of #11367.

 Test Plan: ./validate

 Reviewers: austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1779

 GHC Trac Issues: #11367
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11367#comment:14>
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