[GHC] #15591: Inconsistent kind variable binder visibility between associated and non-associated type families

[GHC]

#15591: Inconsistent kind variable binder visibility between associated and non-
associated type families
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:
                                     |  TypeApplications, TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15592            |  Differential Rev(s):  Phab:D5159
       Wiki Page:                    |
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Comment (by Ryan Scott <ryan.gl.scott@…>):

 In [changeset:"a57fa24746421c0e13d0c09b72cbabea3622779f/ghc"
 a57fa247/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="a57fa24746421c0e13d0c09b72cbabea3622779f"
 Quantify class variables first in associated families' kinds

 Summary:
 Previously, `kcLHsQTyVars` would always quantify class-bound
 variables invisibly in the kinds of associated types, resulting in
 #15591. We counteract this by explicitly passing the class-bound
 variables to `kcLHsQTyVars` and quantifying over the ones that are
 mentioned in the associated type such that (1) they are specified,
 and (2) they come before other kind variables.
 See `Note [Kind variable ordering for associated types]`.

 Test Plan: make test TEST=T15591

 Reviewers: goldfire, simonpj, bgamari

 Reviewed By: simonpj

 Subscribers: rwbarton, carter

 GHC Trac Issues: #15591

 Differential Revision: https://phabricator.haskell.org/D5159
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15591#comment:12>
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