[GHC] #11331: panic! TEST=tc198: lookupVers2 GHC.Stack.Types CallStack

[GHC]

#11331: panic! TEST=tc198: lookupVers2 GHC.Stack.Types CallStack
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        Reporter:  thomie            |                Owner:  gridaphobe
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.11
      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 gridaphobe):

 That actually makes a lot of sense, thanks! The CallStack tycon is wired-
 in, so the type-checker wouldn't have to load GHC.Types.Stack. The datacon
 is not, nor is the newer pushCallStack function we use in the desugarer,
 so that's why it would be loaded during desugaring.

 In this case we're not generating any CallStacks, so dsEvCallStack is not
 called, so the module is not loaded. Hrm.. What is the usual rule for
 loading modules that contain wired-in things? Or is it even necessary to
 fingerprint a wired-in thing?

 (By the way, how ''did'' you figure out what was triggering the load?)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11331#comment:4>
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