[GHC] #11371: Bogus in-scope set in substitutions

[GHC]

#11371: Bogus in-scope set in substitutions
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        Reporter:  simonpj           |                Owner:  niteria
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11360            |  Differential Rev(s):  phab:D1792,
       Wiki Page:                    |  phab:D1801, phab:D1802
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Comment (by Bartosz Nitka <niteria@…>):

 In [changeset:"1757dd8ebed0732018319e43e6468b868a6aceeb/ghc"
 1757dd8e/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="1757dd8ebed0732018319e43e6468b868a6aceeb"
 Don't recompute some free vars in lintCoercion

 As pointed out by @simonpj on D2044 we don't need
 to compute the free vars of the range of the substitution
 as most of them are already carried by the monad.
 This should be a tiny performance improvement over the version
 from before D2044.

 Also removes an extra function that is now unnecessary.

 Test Plan: ./validate && ./validate --slow

 Reviewers: goldfire, simonpj, austin, bgamari

 Reviewed By: simonpj

 Subscribers: thomie, simonmar, simonpj

 Differential Revision: https://phabricator.haskell.org/D2060

 GHC Trac Issues: #11371
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11371#comment:57>
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