INTERNAL ERROR: depTypeExp

hello,

here is (a simplifed version of) what i run into while playing with 
continuations.
i guess the important thing is the type sugnature, not the definition.

 > f :: ((forall b. b) -> Int) -> Int
 > f = f

on this hugs (version May 2003) reports:
INTERNAL ERROR: depTypeExp

i am a bit rusty on how one calculates the rank of a type,
but perhaps this is a rank-3 type?

bye iavor