[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 simonpj):

 We have
 {{{
 data STRef s a = STRef (MutVar# s a)
 newtype IORef a = IORef (STRef RealWorld a)
 data Handle__ = H !(IORef Char)
 }}}
 Indeed the pointer to the `MutVarf` is untagged; but heisenbug is claiming
 that the pointer to the `IORef`, stored in the `Handle__` is untagged.
 And that pointer should ''certainly'' be tagged.   Smoking gun, I say, if
 I have correctly understood the claim.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14626#comment:30>
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