[GHC] #14561: Panic on levity polymorphic very unsafe coerce

[GHC]

#14561: Panic on levity polymorphic very unsafe coerce
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:
                                     |  LevityPolymorphism
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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Comment (by simonmar):

 There are lots of `unsafeCoerce#` in the GHCi debugger
 (`RtClosureInspect`) where we need to coerce unknown but pointed types
 into unpointed types like `MutVar#`.  There's another instance of this
 kind of coercion in `newStablePtrPrimMVar` in base.

 I don't know of any places where we legitimately coerce between boxed and
 unboxed types, but I think it would be nice if we could retain the ability
 to do so, for debugging (e.g. printing out pointer values) & general
 hacking purposes.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14561#comment:4>
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