[GHC] #13251: Must perform family consistency check on non-imported identifiers

[GHC]

#13251: Must perform family consistency check on non-imported identifiers
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        Reporter:  ezyang            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ezyang):

 Yes, I think that's along the ideas of what we ought to do, although Simon
 thinks it would be simpler if we didn't do the family instance checks
 until the very end of the entire module.

 Template Haskell NameG on an external package which we don't actually
 depend on is an interesting problem. One possibility is that we should
 validate these references, and complain if the identifier comes from
 something we didn't depend on (I guess this is the preload set?) I haven't
 thought too carefully about this.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13251#comment:4>
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