[GHC] #14626: No need to enter a scrutinised value

[GHC]

#14626: No need to enter a scrutinised value
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        Reporter:  heisenbug         |                Owner:  heisenbug
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  performance
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13861            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by heisenbug):

 Replying to [comment:39 simonpj]:
 > Alex, you've nailed it.  Thank you!  I'll think about what to do. I'm
 astonished it hasn't led to more serious problems already.

 I'll second that! Great work Alex! Will there be another ticket I can
 block this one on?

 Simon, do you think we should insert taggedness-checks into runtime when
 the compiler (resp. a binary) is built with some debug flag? My current
 solution is rather weak and won't work for constructors that have
 constraints (e.g. class dictionaries) in them. It may be a good way to
 detect similar hiccups in the future. I'll happily invest some effort to
 make my current checks water-proof, though.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14626#comment:40>
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