[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 Bartosz Nitka <niteria@…>):

 In [changeset:"dbf72dbc6e49b3db7f2337a7a41e95c1d0169163/ghc"
 dbf72dbc/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="dbf72dbc6e49b3db7f2337a7a41e95c1d0169163"
 Build the substitution correctly in piResultTy

 This fixes a bug where piResultTy created
 substitutions that would violate both of the invariants
 in Note [The substitution invariant].

 Test Plan: ./validate --slow

 Reviewers: goldfire, simonpj, austin, bgamari

 Reviewed By: simonpj, bgamari

 Subscribers: simonmar, thomie

 Differential Revision: https://phabricator.haskell.org/D1855

 GHC Trac Issues: #11371
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11371#comment:26>
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