[GHC] #13594: Typechecker behavior w.r.t. BangPatterns and nested foralls has changed in 8.2

[GHC]

#13594: Typechecker behavior w.r.t. BangPatterns and nested foralls has changed in
8.2
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        Reporter:  RyanGlScott       |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  8.2.1-rc2
  checker)                           |             Keywords:  BangPatterns,
      Resolution:                    |  RankNTypes
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3525
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"372995364c52eef15066132d7d1ea8b6760034e6/ghc"
 37299536/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="372995364c52eef15066132d7d1ea8b6760034e6"
 Treat banged bindings as FunBinds

 This reworks the HsSyn representation to make banged variable patterns
 (e.g. !x = e) be represented as FunBinds instead of PatBinds, adding a
 flag to
 FunRhs to record the bang.

 Fixes #13594.

 Reviewers: austin, goldfire, alanz, simonpj

 Reviewed By: simonpj

 Subscribers: simonpj, rwbarton, thomie, mpickering

 Differential Revision: https://phabricator.haskell.org/D3525
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13594#comment:9>
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