[GHC] #10871: Implement "buildable" interface files which can be directly compiled without source

[GHC]

#10871: Implement "buildable" interface files which can be directly compiled
without source
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        Reporter:  ezyang            |                   Owner:  ezyang
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.11
      Resolution:                    |                Keywords:  backpack
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonpj):

 Tidying does a number of things, listed at the top of `TidyPgm`.

 I have not thought this through fully, but my guess is that most of them
 aren't what we want for a fat interface file; e.g. dropping rules; the
 whole `findExternalIds` thing; injecting implicit bindings, etc.

 But we probably do need one aspect of tidying, namely to rename things.
 Consider `\x_12 \x_14. x_12`, where the `_n` part is the unique.  When we
 serialise into an interface file we drop the unique, so it's important
 that the `OccNames` don't shadow.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10871#comment:4>
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