[GHC] #15195: Merge -XPolyKinds with -XTypeInType

[GHC]

#15195: Merge -XPolyKinds with -XTypeInType
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:  int-index
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  GHCProposal
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4748
       Wiki Page:                    |
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Comment (by Richard Eisenberg <rae@…>):

 In [changeset:"d650729f9a0f3b6aa5e6ef2d5fba337f6f70fa60/ghc" d650729/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="d650729f9a0f3b6aa5e6ef2d5fba337f6f70fa60"
 Embrace -XTypeInType, add -XStarIsType

 Summary:
 Implement the "Embrace Type :: Type" GHC proposal,
 .../ghc-proposals/blob/master/proposals/0020-no-type-in-type.rst

 GHC 8.0 included a major change to GHC's type system: the Type :: Type
 axiom. Though casual users were protected from this by hiding its
 features behind the -XTypeInType extension, all programs written in GHC
 8+ have the axiom behind the scenes. In order to preserve backward
 compatibility, various legacy features were left unchanged. For example,
 with -XDataKinds but not -XTypeInType, GADTs could not be used in types.
 Now these restrictions are lifted and -XTypeInType becomes a redundant
 flag that will be eventually deprecated.

 * Incorporate the features currently in -XTypeInType into the
   -XPolyKinds and -XDataKinds extensions.
 * Introduce a new extension -XStarIsType to control how to parse * in
   code and whether to print it in error messages.

 Test Plan: Validate

 Reviewers: goldfire, hvr, bgamari, alanz, simonpj

 Reviewed By: goldfire, simonpj

 Subscribers: rwbarton, thomie, mpickering, carter

 GHC Trac Issues: #15195

 Differential Revision: https://phabricator.haskell.org/D4748
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15195#comment:3>
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