Implicit Params cause core dump!

GHC 5.0 compiles the following to a program that dumps
core:

main = putStr $ show $ foo with ?x = 13

foo :: (?x :: Int) => Int
foo = ?x

Trac metadata

Trac field	Value
Version	5.0
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	ResolvedFixed
Component	Compiler
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