[GHC] #9739: GHC 7.8 chokes on recursive classes

[GHC]

#9739: GHC 7.8 chokes on recursive classes
-------------------------------------+-------------------------------------
        Reporter:  bitonic           |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  7.10.1
       Component:  Compiler (Type    |              Version:  7.9
  checker)                           |
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  crash                              |  typecheck/should_fail/T9739
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
-------------------------------------+-------------------------------------

Comment (by Matthew Pickering <matthewtpickering@…>):

 In [changeset:"44640af7afa1a01ff2e2357f7c1436b4804866fc/ghc"
 44640af7/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="44640af7afa1a01ff2e2357f7c1436b4804866fc"
 Allow as-patterns in pattern synonym declarations.

 We can allow them if they contain no free variables. This patch just
 allows
 them in one direction and not to be used as builders as the original
 ticket
 suggests.

 Test Plan: ./validate

 Reviewers: austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1666

 GHC Trac Issues:  #9739

 Conflicts:
         testsuite/tests/patsyn/should_fail/all.T
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9739#comment:13>
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