[GHC] #12523: Constructor info tables generated by GHCi don't return tagged pointers

[GHC]

#12523: Constructor info tables generated by GHCi don't return tagged pointers
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        Reporter:  mniip             |                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:  GHCi crash        |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * cc: simonmar (added)


Comment:

 Yes, tagging really is part of the return convention for data
 constructors, so I'm a bit surprised that GHCi gets away without it.

 Is `unsafeCoerce` really part of this?  What happens for
 {{{
 unX (X "foo")
 }}}
 or
 {{{
 unX (id (X "foo"))
 }}}
 ?  Why would it be different to what happens with `unsafeCoerce`?

 I'm adding Simon Marlow (king of GHCi) in cc.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12523#comment:1>
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