Re: [GHC] #12045: Visible kind application

1 Nov 2018

      #12045: Visible kind application
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  mnguyen
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
                                     |  TypeApplications TypeInType
                                     |  GHCProposal
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:  14579
 Related Tickets:  #15782            |  Differential Rev(s):  Phab:D5229
       Wiki Page:                    |
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Comment (by Richard Eisenberg ):

 In [changeset:"255d2e323a8879a7296a5ab94e6cc49023e2c86e/ghc" 255d2e3/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="255d2e323a8879a7296a5ab94e6cc49023e2c86e"
 Fix embarrassing, egregious bug in roles of (->)

 Previously, I had inexplicably decided that (->)'s roles
 were all Representational. But, of course, its first two
 parameters are *dependent* RuntimeReps. All dependent parameters
 have a Nominal role, because all roles in kinds are Nominal.

 Fix is easy, but I have no idea how the world hasn't come
 crashing down before now.

 This was found while investigating #15801, which requires
 visible type application in types to observe. Hence, the test
 case will come with the main patch for #12045.
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12045#comment:20
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