[GHC] #8958: Allow role inference on datatype contexts

[GHC]

#8958: Allow role inference on datatype contexts
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        Reporter:  goldfire                    |            Owner:
            Type:  feature request             |  goldfire
        Priority:  normal                      |           Status:  closed
       Component:  Compiler                    |        Milestone:  7.8.1
      Resolution:  fixed                       |          Version:
Operating System:  Unknown/Multiple            |  7.8.1-rc2
 Type of failure:  None/Unknown                |         Keywords:
       Test Case:  roles/should_compile/T8958  |     Architecture:
        Blocking:                              |  Unknown/Multiple
                                               |       Difficulty:  Unknown
                                               |       Blocked By:
                                               |  Related Tickets:
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Comment (by simonpj):

 Fair enough. You are arguing that nothing belongs in the user manual
 because there is no special compiler behaviour.

 Yet a user approaching roles might still miss all of this.  We have a
 mechanism for this: a wike page at Haskell.org.   The "Documentation" link
 on [http://www.haskell.org/ghc/ GHC's home page] gets you
 [http://www.haskell.org/haskellwiki/GHC here]. The "Collaborative
 documentation" section is for user-level documentation about how to use
 GHC, above and beyond the user manual.  In particular there is user-level
 documentation for [http://www.haskell.org/haskellwiki/GHC/Type_system type
 system extensions].  So that would be an excellent place for some user-
 facing documentation about roles, including a pointer to your library.

 I'm not suggesting that it's your responsibility to write such a page; but
 starting one, with an invitation to others to add more, would be an
 excellent move.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8958#comment:7>
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