[GHC] #13102: orphan family instances can leak through the EPS in --make mode

[GHC]

#13102: orphan family instances can leak through the EPS in --make mode
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        Reporter:  rwbarton          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rwbarton):

 > Wired-in things are below everything

 Right, so this becomes a constraint that we have to adhere to under this
 plan. And it's a constraint I was intending to violate with the large
 tuples Generic stuff (tuples are wired-in, and I was going to use
 `deriving Generic` in the module that defines them). I'm not so happy with
 that exact idea any more for other reasons, so probably it shouldn't stop
 us from this plan.

 > Checking family-instance consistency. Here I am not so clear, but we
 should write down the plan.

 I started writing up the plan in d6fd7922332a16fb958d3bf2c21ed792d12c98a7.

 Note that there is another point related to your item 2 here, in that (at
 least in principle) we should only check consistency of the new instances
 with the instances we transitively import, not any old instances we happen
 to know about.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13102#comment:6>
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