[GHC] #9729: GHCi accepts invalid programs when recompiling

[GHC]

#9729: GHCi accepts invalid programs when recompiling
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              Reporter:  crockeea    |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  GHCi        |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:  GHC         |       Blocked By:
  accepts invalid program            |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Changes (by simonpj):

 * cc: ezyang (added)


Comment:

 I think your hypothesis is likely right.  It's a long-standing deficiency
 in GHCi that it doesn't make instance declarations scope correctly, or
 (words) predictably.  Edward Yang is thinking about ways to fix this.

 Can you just be more explicit about what module `B` looks like after the
 edit?  What, precisely, does "remove the constraint" mean?

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9729#comment:2>
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