[GHC] #8489: clean up dependency and usages handling in interface files

[GHC]

#8489: clean up dependency and usages handling in interface files
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              Reporter:  errge       |            Owner:  errge
                  Type:  task        |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Template    |          Version:  7.7
  Haskell                            |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Moderate (less
  Unknown/Multiple                   |  than a day)
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by errge):

 If I remember correctly the difference is not the package boundary, but
 the compilation unit boundary.  So if you compile your modules with
 different GHC invocations by using -c instead of --make, then you will not
 have the `usg_exports` either, am I right?

 If that is the case I prefer us to do the right fix and include this
 information in the interfaces files and do not introduce different
 behavior depending on compilation technique in the meantime.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8489#comment:7>
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