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

[GHC]

#11371: Bogus in-scope set in substitutions
-------------------------------------+-------------------------------------
        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
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"73935326e0cf85ed077b9ab7dd8f197d39e2cd5b/ghc"
 73935326/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="73935326e0cf85ed077b9ab7dd8f197d39e2cd5b"
 Use a correct substitution in tcInstType

 `ty` doesn't have to be a closed type, so we need to add its
 free vars to the in-scope set. They don't seem to be
 available anywhere nearby, so we have to compute them.

 Test Plan: ./validate

 Reviewers: goldfire, austin, bgamari, simonpj

 Reviewed By: simonpj

 Subscribers: thomie, simonmar

 Differential Revision: https://phabricator.haskell.org/D2042

 GHC Trac Issues: #11371
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11371#comment:54>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler