Empty a set when ExceptWith is passed the set itself

Containers.Test/ContiguousSetTests.cs

@@ -297,6 +297,16 @@ public void ExceptWith_RemovesCommonElements()
 		Assert.DoesNotContain(4, set1);
 	}
 
+	[TestMethod]
+	public void ExceptWith_Self_EmptiesSet()
+	{
+		ContiguousSet<int> set = [.. new int[] { 1, 2, 3, 4 }];
+
+		set.ExceptWith(set);
+
+		Assert.IsEmpty(set);
+	}
+
 	[TestMethod]
 	public void SymmetricExceptWith_KeepsUniqueElements()
 	{

Containers.Test/InsertionOrderSetTests.cs

@@ -310,6 +310,16 @@ public void ExceptWith_RemovesCommonElements()
 		Assert.AreEqual(3, set1.ElementAt(1));
 	}
 
+	[TestMethod]
+	public void ExceptWith_Self_EmptiesSet()
+	{
+		InsertionOrderSet<int> set = [.. new int[] { 1, 2, 3, 4 }];
+
+		set.ExceptWith(set);
+
+		Assert.IsEmpty(set);
+	}
+
 	[TestMethod]
 	public void WorksWithStrings_MaintainsInsertionOrder()
 	{

Containers.Test/OrderedSetTests.cs

@@ -373,6 +373,16 @@ public void ExceptWith_RemovesSpecifiedElements()
 		Assert.AreSequenceEqual(expected, set1);
 	}
 
+	[TestMethod]
+	public void ExceptWith_Self_EmptiesSet()
+	{
+		OrderedSet<int> set = [.. new int[] { 1, 2, 3, 4 }];
+
+		set.ExceptWith(set);
+
+		Assert.IsEmpty(set);
+	}
+
 	[TestMethod]
 	public void ExceptWith_NullCollection_ThrowsArgumentNullException()
 	{

Containers/ContiguousSet.cs

@@ -371,6 +371,13 @@ public void ExceptWith(IEnumerable<T> other)
 	{
 		Ensure.NotNull(other);
 
+		// Removing while enumerating this set would skip or throw; excepting a set from itself empties it
+		if (ReferenceEquals(other, this))
+		{
+			Clear();
+			return;
+		}
+
 		foreach (T item in other)
 		{
 			Remove(item);

Containers/InsertionOrderSet.cs

@@ -300,6 +300,13 @@ public void ExceptWith(IEnumerable<T> other)
 	{
 		Ensure.NotNull(other);
 
+		// Removing while enumerating this set would skip or throw; excepting a set from itself empties it
+		if (ReferenceEquals(other, this))
+		{
+			Clear();
+			return;
+		}
+
 		foreach (T item in other)
 		{
 			Remove(item);

Containers/OrderedSet.cs

@@ -381,6 +381,13 @@ public void ExceptWith(IEnumerable<T> other)
 	{
 		Ensure.NotNull(other);
 
+		// Removing while enumerating this set would skip or throw; excepting a set from itself empties it
+		if (ReferenceEquals(other, this))
+		{
+			Clear();
+			return;
+		}
+
 		foreach (T item in other)
 		{
 			Remove(item);