'Rng.gen_range called with low >= high'

[twittner]

This can happen due to invalid casts from quickcheck::Gen::size of type usize to various other integer types with a value range smaller than usize (cf. quickcheck::arbitrary::unsigned_arbitrary).

Test case:

#[test]
fn test() {
    fn prop(_: u8) -> bool { true }

    QuickCheck::new()
        .gen(StdGen::new(rand::thread_rng(), 1024))
        .quickcheck(prop as fn(u8) -> bool)
}

[BurntSushi]

Thanks for the report!