[GHC] #11396: deriving Ix with custom ifThenElse causes "Bad call to tagToEnum#"

[GHC]

#11396: deriving Ix with custom ifThenElse causes "Bad call to tagToEnum#"
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        Reporter:  Lemming           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1-rc1
      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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Changes (by thomie):

 * priority:  normal => highest
 * milestone:   => 8.0.1


Comment:

 Regression. Reproducible with HEAD.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11396#comment:1>
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