bug in the product iterator

[ghost]

I'm not completely sure if this is intended, but product from Iterators.product currently has the following behavior:

First up, the nice case:

for i in product(1:3,1:2); println(i); end
(1,1)
(2,1)
(3,1)
(1,2)
(2,2)
(3,2)

However, suppose we switch the second argument to a single element:

for i in product(1:3,1); println(i); end
(1,1)
(2,1)
(3,1)
(1,1)
(2,1)
(3,1)

Are the repeated elements desired here? A singleton in the first argument produces an even more interesting result:

for i in product(1,1:3); println(i); end
(1,1)
(1,1)
(1,2)
(1,3)