[GHC] #13394: PatternSynonyms/OverloadedStrings regression in GHC HEAD

[GHC]

#13394: PatternSynonyms/OverloadedStrings regression in GHC HEAD
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
                                     |  PatternSynonyms
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"8e053700f9357c1b9030c406130062795ae5015c/ghc" 8e05370/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="8e053700f9357c1b9030c406130062795ae5015c"
 Join points can be levity-polymorphic

 It's ok to have a levity-polymorphic join point, thus
    let j :: r :: TYPE l = blah
    in ...

 Usually we don't allow levity-polymorphic binders, but join points
 are different because they are not first class.  I updated the
 invariants in CoreSyn.

 This commit fixes Trac #13394.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13394#comment:2>
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