[GHC] #15599: typeclass inference depends on whether a module is exposed.

[GHC]

#15599: typeclass inference depends on whether a module is exposed.
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        Reporter:  gleachkr          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.3
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mpickering):

 Here's how to reproduce it without any of these package db gubbins.

 1. Clone `https://github.com/gleachkr/GHC-Repro.git`
 2. `echo "test" | cabal repl` - observe that `Flag {checkFlag = True}`
 3. `cabal install .`
 4. `echo "test" | ghci src/Test/Good.hs` - observe that `Flag {checkFlag =
 False}`

 So the same module used in two different ways uses two different
 instances.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15599#comment:8>
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