[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:  closed
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  8.2.1-rc2
  checker)                           |             Keywords:  BangPatterns,
      Resolution:  fixed             |  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:D3661
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"af89d6872da2e00be738e1ac541346cd84e6d141/ghc" af89d68/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="af89d6872da2e00be738e1ac541346cd84e6d141"
 Reject top-level banged bindings

 Bizarrely, we were not rejecting
   !x = e

 Fix:

 * In the test in DsBinds.dsTopLHsBinds, use isBangedHsBind, not
   isBangedPatBind.  (Indeed the latter dies altogther.)

 * Implement isBangedHsBind in HsUtils;
   be sure to handle AbsBinds

 All this was shown up by Trac #13594
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13594#comment:24>
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