Merge pull request #2162 from jasonwoods-7/master

Fix for SymmetricExcept when using equality comparer.

Author: stephentoub

src/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableHashSet`1.cs

@@ -852,7 +852,7 @@ private static MutationResult SymmetricExcept(IEnumerable<T> other, MutationInpu
         {
             Requires.NotNull(other, "other");
 
-            var otherAsSet = Empty.Union(other);
+            var otherAsSet = ImmutableHashSet.CreateRange(origin.EqualityComparer, other);
 
             int count = 0;
             var result = SortedInt32KeyNode<HashBucket>.EmptyNode;

src/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableSortedSet`1.cs

@@ -278,7 +278,7 @@ public ImmutableSortedSet<T> SymmetricExcept(IEnumerable<T> other)
         {
             Requires.NotNull(other, "other");
 
-            var otherAsSet = ImmutableSortedSet<T>.Empty.Union(other);
+            var otherAsSet = ImmutableSortedSet.CreateRange(_comparer, other);
 
             var result = this.Clear();
             foreach (T item in this)

src/System.Collections.Immutable/tests/ImmutableHashSetTest.cs

@@ -163,6 +163,19 @@ public void DebuggerAttributesValid()
             DebuggerAttributes.ValidateDebuggerTypeProxyProperties(ImmutableHashSet.Create<int>(1, 2, 3));
         }
 
+        [Fact]
+        public void SymmetricExceptWithComparerTests()
+        {
+            var set = ImmutableHashSet.Create<string>("a").WithComparer(StringComparer.OrdinalIgnoreCase);
+            var otherCollection = new[] {"A"};
+
+            var expectedSet = new HashSet<string>(set, set.KeyComparer);
+            expectedSet.SymmetricExceptWith(otherCollection);
+
+            var actualSet = set.SymmetricExcept(otherCollection);
+            CollectionAssertAreEquivalent(expectedSet.ToList(), actualSet.ToList());
+        }
+
         protected override IImmutableSet<T> Empty<T>()
         {
             return ImmutableHashSet<T>.Empty;

src/System.Collections.Immutable/tests/ImmutableSortedSetTest.cs

@@ -368,6 +368,19 @@ public void DebuggerAttributesValid()
             DebuggerAttributes.ValidateDebuggerDisplayReferences(rootNode);
         }
 
+        [Fact]
+        public void SymmetricExceptWithComparerTests()
+        {
+            var set = ImmutableSortedSet.Create<string>("a").WithComparer(StringComparer.OrdinalIgnoreCase);
+            var otherCollection = new[] {"A"};
+
+            var expectedSet = new SortedSet<string>(set, set.KeyComparer);
+            expectedSet.SymmetricExceptWith(otherCollection);
+
+            var actualSet = set.SymmetricExcept(otherCollection);
+            CollectionAssertAreEquivalent(expectedSet.ToList(), actualSet.ToList());
+        }
+
         protected override IImmutableSet<T> Empty<T>()
         {
             return ImmutableSortedSet<T>.Empty;