[GHC] #13618: Reified data family instances type variables not related to value constructor fields

[GHC]

#13618: Reified data family instances type variables not related to value
constructor fields
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        Reporter:  glguy             |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1-rc1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3505
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"b2c38d6b4003d3dda60d15204283da5aab15c2ec/ghc" b2c38d6/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="b2c38d6b4003d3dda60d15204283da5aab15c2ec"
 Make the tyvars in TH-reified data family instances uniform

 It turns out we were using two different sets of type variables when
 reifying data family instances in Template Haskell. We were using the
 tyvars quantifying over the instance itself for the LHS, but using the
 tyvars quantifying over the data family instance constructor for the
 RHS. This commit uses the instance tyvars for both the LHS and the RHS,
 fixing #13618.

 Test Plan: make test TEST=T13618

 Reviewers: goldfire, austin, bgamari

 Reviewed By: goldfire, bgamari

 Subscribers: rwbarton, thomie

 GHC Trac Issues: #13618

 Differential Revision: https://phabricator.haskell.org/D3505
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13618#comment:2>
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