[GHC] #15589: Always promoting metavariables during type inference may be wrong

[GHC]

#15589: Always promoting metavariables during type inference may be wrong
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Ningning Xie <xnningxie@…>):

 In [changeset:"3905c3c07ba2735e5b3d2dc3389272d5dbb1c503/ghc" 3905c3c/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="3905c3c07ba2735e5b3d2dc3389272d5dbb1c503"
 Update core-spec for Coercion Quantification

 Summary:
 Update details for `ForAllTy` and `ForAllCo` in core-spec, as they
 can now quantify over coercion variables.

 Test Plan: Please read core-spec.pdf

 Reviewers: goldfire, simonpj, bgamari

 Reviewed By: goldfire

 Subscribers: rwbarton, carter

 GHC Trac Issues: #15497, #15589

 Differential Revision: https://phabricator.haskell.org/D5247
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15589#comment:14>
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