[GHC] #4012: Compilation results are not deterministic

[GHC]

#4012: Compilation results are not deterministic
-------------------------------------+-------------------------------------
        Reporter:  kili              |                Owner:  niteria
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  6.12.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:  11362             |             Blocking:
 Related Tickets:  #10424            |  Differential Rev(s):  Phab:D910,
                                     |  Phab:D1073, Phab:D1133, Phab:D1192,
                                     |  Phab:D1268, Phab:D1360, Phab:D1373,
       Wiki Page:                    |  Phab:D1396, Phab:D1457, Phab:D1468,
  DeterministicBuilds                |  Phab:D1487, Phab:D1504, Phab:D1508
-------------------------------------+-------------------------------------

Comment (by Bartosz Nitka <niteria@…>):

 In [changeset:"c9bcaf3165586ac214fa694e61c55eb45eb131ab/ghc"
 c9bcaf31/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="c9bcaf3165586ac214fa694e61c55eb45eb131ab"
 Kill varSetElemsWellScoped in quantifyTyVars

 varSetElemsWellScoped introduces unnecessary non-determinism in
 inferred type signatures.
 Removing this instance required changing the representation of
 TcDepVars to use deterministic sets.
 This is the last occurence of varSetElemsWellScoped, allowing me to
 finally remove it.

 Test Plan:
 ./validate
 I will update the expected outputs when commiting, some reordering
 of type variables in types is expected.

 Reviewers: goldfire, simonpj, austin, bgamari

 Reviewed By: simonpj

 Subscribers: thomie, simonmar

 Differential Revision: https://phabricator.haskell.org/D2135

 GHC Trac Issues: #4012
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:150>
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