[GHC] #8177: Roles for type families

[GHC]

#8177: Roles for type families
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              Reporter:  simonpj     |            Owner:  goldfire
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  ⊥
             Component:  Compiler    |          Version:  7.6.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by goldfire):

 In trying to sweep up remaining tickets assigned to me before the feature
 freeze, I came across this one.

 In comment:5, I ask for real users who want role annotations for type
 and/or data families (and/or their respective instances) to do real work
 -- preferably with an example of said real work. Though two people came
 out of the woodwork and tried to meet this need, neither one really
 qualifies:

 - The example from jwlato requires something fundamentally different from
 this ticket -- the ability to do representational matching on families.
 That, essentially, has been moved to #9112. The solution there may also
 require getting this ticket sorted out, but I don't think this ticket is
 the blocking issue.

 - The example from dmmclean is also, by dmmclean's own admission, not
 applicable here.

 Fixing this would take several days worth of work, and days are precious.
 So I'm going to let this one slip unless convinced otherwise. Thanks!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8177#comment:27>
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