[GHC] #13237: Extend TH with addModCStub

[GHC]

#13237: Extend TH with addModCStub
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        Reporter:                    |                Owner:
  facundo.dominguez                  |  facundo.dominguez
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Template Haskell  |              Version:  8.0.1
      Resolution:                    |             Keywords:  inline-c
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3106
       Wiki Page:                    |
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Comment (by rwbarton):

 Even if that scenario is not possible already, it will be possible with
 this change, so it should be addressed.

 Anyways, I think it's an equivalent scenario to one in which the
 implementation of an ordinary function has changed, but in a way that
 doesn't affect any information that appears in the interface file (e.g.
 its type or unfolding); and then that function is used in a TH splice in
 another module. I assume that one of the interface file hashes takes this
 into account, so it should also take the `addModCStub` calls into account.
 (Or possibly we don't handle this scenario correctly at present.)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13237#comment:12>
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