I undestand that for BigInt there is no hard limit like for Int64 for example but the lack of a value seems to cause a problem with rationalize() at line 69 where it is not possible to get a Rational with BigInt num and den. It seems to me that line 69 of rational.jl shall special case the BigInt or that BigInt shall return something valid for typemin/typemax.
at line 69: if x < typemin(T); return -one(T)//zero(T); end
