[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 rwbarton):

 Replying to [comment:22 dmcclean]:
 > Hmmm.
 >
 > I was concerned there for a second, because actually `Quantity'` won't
 be in scope for my users. Its not exported from the module because you can
 use it to do nefarious things.

 BTW I'm confused by this comment, because the things you can do with
 `Quantity'` are just the things you can do with `coerce`, no?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8177#comment:24>
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