debugger gives "Can't unify" when stopped at an exception

Presumably due to exceptions now using existential types, the GHCi debugger now gives:

ghc: panic! (the 'impossible' happened)
  (GHC version 6.9.20080731 for x86_64-unknown-linux):
   Can't unify

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

when it stops at an exception. See break011 and break024 for testcases.

Trac metadata

Trac field	Value
Version	6.8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
Test case	break011, break024
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Operating system	Unknown
Architecture	Unknown