[GHC] #2721: Newtype deriving doesn't work with type families

[GHC]

#2721: Newtype deriving doesn't work with type families
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        Reporter:  rl                |                Owner:
            Type:  feature request   |               Status:  patch
        Priority:  lowest            |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  6.10.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  deriving/should_fail/T2721
      Blocked By:                    |             Blocking:
 Related Tickets:  #8165             |  Differential Rev(s):  Phab:D2636
       Wiki Page:                    |
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Comment (by Ryan Scott <ryan.gl.scott@…>):

 In [changeset:"630d88176e8dd3ccc269451bca8f55398ef5265c/ghc"
 630d8817/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="630d88176e8dd3ccc269451bca8f55398ef5265c"
 Allow GeneralizedNewtypeDeriving for classes with associated type families

 Summary:
 This implements the ability to derive associated type family instances
 for newtypes automatically using `GeneralizedNewtypeDeriving`. Refer to
 the
 users' guide additions for how this works; I essentially follow the
 pattern
 laid out in https://ghc.haskell.org/trac/ghc/ticket/8165#comment:18.

 Fixes #2721 and #8165.

 Test Plan: ./validate

 Reviewers: simonpj, goldfire, austin, bgamari

 Reviewed By: simonpj

 Subscribers: mpickering, thomie

 Differential Revision: https://phabricator.haskell.org/D2636

 GHC Trac Issues: #2721, #8165
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2721#comment:26>
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