[GHC] #7478: setSessionDynFlags does not always work

[GHC]

#7478: setSessionDynFlags does not always work
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    Reporter:  edsko             |       Owner:  simonmar        
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:  7.6.2           
   Component:  Compiler          |     Version:  7.6.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Changes (by simonmar):

  * owner:  => simonmar
  * difficulty:  => Unknown
  * milestone:  => 7.6.2


Comment:

 You're getting the `DynFlags` from the cached `ModSummary`.  I think
 there's an easy fix: we should discard the cache in `setSessionDynFlags`.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7478#comment:3>
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