[GHC] #13604: regression in ghc 8.2.1-rc1 (8.2.0.20170404)

[GHC]

#13604: regression in ghc 8.2.1-rc1 (8.2.0.20170404)
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        Reporter:  George            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.2.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I wonder if this bug has the same underlying cause as #13500? The `[flags
 changed]` part makes me suspect so.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13604#comment:4>
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