[GHC] #9265: Extend PackageId to include version dependency information

[GHC]

#9265: Extend PackageId to include version dependency information
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        Reporter:  ezyang            |            Owner:  ezyang
            Type:  feature request   |           Status:  new
        Priority:  high              |        Milestone:
       Component:  Package system    |          Version:  7.9
      Resolution:                    |         Keywords:  backpack
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by rwbarton):

 What about packages that include "cbits" where the calling convention (or
 just semantics) of the C function changes from one version to the next?
 Won't the linker complain or, worse, just pick one? I guess with dynamic
 linking it might work.

 Admittedly, it could already happen that two unrelated packages use
 clashing names for their incompatible "cbits" C functions, but it seems
 rather more likely to occur between one version of a package and the next.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9265#comment:5>
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