[GHC] #3699: Wildcards in type functions

[GHC]

#3699: Wildcards in type functions
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        Reporter:                    |                   Owner:  msosn
  MartijnVanSteenbergen              |
            Type:  feature request   |                  Status:  new
        Priority:  low               |               Milestone:  7.12.1
       Component:  Compiler (Type    |                 Version:  6.10.4
  checker)                           |
      Resolution:                    |                Keywords:  newcomer
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:  Phab:D1092
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"d9d2102ea7f6da1bc3a69fa469b89ea843cb8b02/ghc"
 d9d2102e/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="d9d2102ea7f6da1bc3a69fa469b89ea843cb8b02"
 Support wild cards in data/type family instances

 Handle anonymous wild cards in type or data family instance
 declarations like
 unnamed type variables. For instance (pun intented):

     type family F (a :: *) (b :: *) :: *
     type instance F Int _ = Int

 Is now the same as:

     type family F (a :: *) (b :: *) :: *
     type instance F Int x = Int

 Note that unlike wild cards in partial type signatures, no errors (or
 warnings
 with -XPartialTypeSignatures) are generated for these wild cards, as
 there is
 nothing interesting to report to the user, i.e. the inferred kind.

 Only anonymous wild cards are supported here, named and
 extra-constraints wild
 card are not.

 Test Plan: pass new tests

 Reviewers: goldfire, austin, simonpj, bgamari

 Reviewed By: simonpj, bgamari

 Subscribers: goldfire, thomie

 Differential Revision: https://phabricator.haskell.org/D1092

 GHC Trac Issues: #3699, #10586
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3699#comment:24>
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