[GHC] #16033: Rank-n typechecking regression between GHC 8.4 and 8.6

[GHC]

#16033: Rank-n typechecking regression between GHC 8.4 and 8.6
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler (Type    |              Version:  8.6.3
  checker)                           |
      Resolution:                    |             Keywords:  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):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"a1c3ad0450baedadc223969dd2b09f59872a38e7/ghc" a1c3ad0/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="a1c3ad0450baedadc223969dd2b09f59872a38e7"
 Add solveLocalEqualities to tcHsPatSigType

 This call plain missing, and as a result the casts
 messed up deep-skolemisation in tcSubType

 Fixes Trac #16033
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16033#comment:4>
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