[GHC] #12779: isTrue# doesn't work in ghci anymore

[GHC]

#12779: isTrue# doesn't work in ghci anymore
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        Reporter:  osa1              |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #12718            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rwbarton):

 `isTrue# 123#` isn't allowed. The argument must be `0#` or `1#`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12779#comment:2>
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