API Breaking: Equality tests on LinkedHashSet should be consistent

`LinkedHashSet`'s `PartialEq` / `Eq` implementation is now consistent with
`LinkedHashMap`'s implementation, it is order dependent.

Add some simple tests for this property.

Author: kyren

src/linked_hash_set.rs

@@ -304,12 +304,8 @@ where
     S: BuildHasher,
 {
     #[inline]
-    fn eq(&self, other: &LinkedHashSet<T, S>) -> bool {
-        if self.len() != other.len() {
-            return false;
-        }
-
-        self.iter().all(|key| other.contains(key))
+    fn eq(&self, other: &Self) -> bool {
+        self.len() == other.len() && self.iter().eq(other)
     }
 }
 

tests/linked_hash_map.rs

@@ -496,3 +496,18 @@ fn test_retain() {
     drop(map);
     assert!(c.get() == 4);
 }
+
+#[test]
+fn test_order_equality() {
+    let xs = [1, 2, 3, 4, 5, 6];
+    let mut map1: LinkedHashMap<String, i32> = xs.iter().map(|i| (i.to_string(), *i)).collect();
+    let mut map2: LinkedHashMap<String, i32> = xs.iter().map(|i| (i.to_string(), *i)).collect();
+
+    assert_eq!(map1, map2);
+
+    map1.to_front("4");
+    assert_ne!(map1, map2);
+
+    map2.to_front("4");
+    assert_eq!(map1, map2);
+}

tests/linked_hash_set.rs

@@ -510,3 +510,18 @@ fn to_back_front_order() {
     set.to_front(&3);
     assert_eq!(set.front().copied(), Some(3));
 }
+
+#[test]
+fn test_order_equality() {
+    let xs = [1, 2, 3, 4, 5, 6];
+    let mut set1: LinkedHashSet<i32> = xs.iter().copied().collect();
+    let mut set2: LinkedHashSet<i32> = xs.iter().copied().collect();
+
+    assert_eq!(set1, set2);
+
+    set1.to_front(&4);
+    assert_ne!(set1, set2);
+
+    set2.to_front(&4);
+    assert_eq!(set1, set2);
+}