Make UniformUsize serializable (#1646)

- [x] Added a `CHANGELOG.md` entry


# Motivation
This allows `WeightedIndex<usize>` to be serializable.

Author: aleb

src/block.rs

@@ -557,7 +557,7 @@ mod test {
         }
         rng.next_u32();
 
-        let result = rng.next_u64();
+        let _ = rng.next_u64();
         assert_eq!(rng.index(), 1);
     }
 }

src/impls.rs

@@ -179,39 +179,39 @@ mod test {
     fn test_fill_via_u32_chunks() {
         let src_orig = [1u32, 2, 3];
 
-        let mut src = src_orig;
+        let src = src_orig;
         let mut dst = [0u8; 11];
-        assert_eq!(fill_via_chunks(&mut src, &mut dst), (3, 11));
+        assert_eq!(fill_via_chunks(&src, &mut dst), (3, 11));
         assert_eq!(dst, [1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0]);
 
-        let mut src = src_orig;
+        let src = src_orig;
         let mut dst = [0u8; 13];
-        assert_eq!(fill_via_chunks(&mut src, &mut dst), (3, 12));
+        assert_eq!(fill_via_chunks(&src, &mut dst), (3, 12));
         assert_eq!(dst, [1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 0]);
 
-        let mut src = src_orig;
+        let src = src_orig;
         let mut dst = [0u8; 5];
-        assert_eq!(fill_via_chunks(&mut src, &mut dst), (2, 5));
+        assert_eq!(fill_via_chunks(&src, &mut dst), (2, 5));
         assert_eq!(dst, [1, 0, 0, 0, 2]);
     }
 
     #[test]
     fn test_fill_via_u64_chunks() {
         let src_orig = [1u64, 2];
 
-        let mut src = src_orig;
+        let src = src_orig;
         let mut dst = [0u8; 11];
-        assert_eq!(fill_via_chunks(&mut src, &mut dst), (2, 11));
+        assert_eq!(fill_via_chunks(&src, &mut dst), (2, 11));
         assert_eq!(dst, [1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0]);
 
-        let mut src = src_orig;
+        let src = src_orig;
         let mut dst = [0u8; 17];
-        assert_eq!(fill_via_chunks(&mut src, &mut dst), (2, 16));
+        assert_eq!(fill_via_chunks(&src, &mut dst), (2, 16));
         assert_eq!(dst, [1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0]);
 
-        let mut src = src_orig;
+        let src = src_orig;
         let mut dst = [0u8; 5];
-        assert_eq!(fill_via_chunks(&mut src, &mut dst), (1, 5));
+        assert_eq!(fill_via_chunks(&src, &mut dst), (1, 5));
         assert_eq!(dst, [1, 0, 0, 0, 0]);
     }
 }

src/lib.rs

@@ -764,9 +764,11 @@ mod test {
         let mut rng = rng.unwrap_mut();
 
         assert_eq!(rng.next_u32(), 4);
-        let mut rng2 = rng.re();
-        assert_eq!(rng2.next_u32(), 4);
-        drop(rng2);
+        {
+            let mut rng2 = rng.re();
+            assert_eq!(rng2.next_u32(), 4);
+            // Make sure rng2 is dropped.
+        }
         assert_eq!(rng.next_u32(), 4);
     }
 }