Use a sign test for bools

src/distributions/uniform.rs

@@ -184,7 +184,11 @@ impl Distribution<u128> for Uniform {
 impl Distribution<bool> for Uniform {
     #[inline]
     fn sample<R: Rng+?Sized>(&self, rng: &mut R) -> bool {
-        rng.next_u32() & 1 == 1
+        // We can compare against an arbitrary bit of an u32 to get a bool.
+        // Because the least significant bits of a lower quality RNG can have
+        // simple patterns, we compare against the most significant bit. This is
+        // easiest done using a sign test.
+        (rng.next_u32() as i32) < 0
     }
 }