[System] Use generic equality comparer in Find/FindLast methods. Fixes #5245

2 files changed, 58 insertions, 29 deletions

diff --git a/mcs/class/System/System.Collections.Generic/LinkedList.cs b/mcs/class/System/System.Collections.Generic/LinkedList.cs
index 4f95b0c54c8..de67153fc0c 100644
--- a/mcs/class/System/System.Collections.Generic/LinkedList.cs
+++ b/mcs/class/System/System.Collections.Generic/LinkedList.cs
@@ -188,18 +188,7 @@ namespace System.Collections.Generic
 		
 		public bool Contains (T value)
 		{
-			LinkedListNode <T> node = first;
-			if (node == null)
-				return false;
-			do
-			{
-				if (value.Equals (node.Value))
-					return true;
-				node = node.forward;
-			}
-			while (node != first);
-
-			return false;
+			return Find (value) != null;
 		}
 		
 		public void CopyTo (T [] array, int index)
@@ -225,35 +214,44 @@ namespace System.Collections.Generic
 			while (node != first);
 		}
 		
-		public LinkedListNode <T> Find (T value)
+		public LinkedListNode<T> Find (T value)
 		{
-			LinkedListNode <T> node = first;
+			var node = first;
 			if (node == null)
 				return null;
-			do
-			{
-				if ( (value == null && node.Value == null) || 
-				     (value != null && value.Equals (node.Value)) )
-					return node;
+
+			do {
+				if (value == null) {
+					if (node.Value == null)
+						return node;
+				} else {
+					if (EqualityComparer<T>.Default.Equals (node.Value, value))
+						return node;
+				}
+
 				node = node.forward;
-			}
-			while (node != first);
+			} while (node != first);
 
 			return null;
 		}
 		
-		public LinkedListNode <T> FindLast (T value)
+		public LinkedListNode<T> FindLast (T value)
 		{
-			LinkedListNode <T> node = first;
+			var node = first;
 			if (node == null)
 				return null;
-			do
-			{
+
+			do {
 				node = node.back;
-				if (value.Equals (node.Value))
-					return node;
-			}
-			while (node != first);
+
+				if (value == null) {
+					if (node.Value == null)
+						return node;
+				} else {
+					if (EqualityComparer<T>.Default.Equals (node.Value, value))
+						return node;
+				}
+			} while (node != first);
 
 			return null;
 		}
diff --git a/mcs/class/System/Test/System.Collections.Generic/LinkedListTest.cs b/mcs/class/System/Test/System.Collections.Generic/LinkedListTest.cs
index f5605744bdd..ad898b102dd 100644
--- a/mcs/class/System/Test/System.Collections.Generic/LinkedListTest.cs
+++ b/mcs/class/System/Test/System.Collections.Generic/LinkedListTest.cs
@@ -12,6 +12,24 @@ namespace MonoTests.System.Collections.Generic
 	[TestFixture]
 	public class LinkedListTest
 	{
+		class EquatableValue : IEquatable<EquatableValue>
+		{
+			public readonly string Value;
+
+			public EquatableValue (string value)
+			{
+				this.Value = value;
+			}
+
+			public bool Equals (EquatableValue other)
+			{
+				if (other == null)
+					return false;
+
+				return string.Equals (Value, other.Value, StringComparison.OrdinalIgnoreCase);
+			}
+		}
+
 		LinkedList <int> intlist;
 		LinkedList <string> strings;
 
@@ -280,6 +298,19 @@ namespace MonoTests.System.Collections.Generic
 			Assert.AreEqual ("efgh", li.Last.Value);
 			Assert.AreEqual ("abcd", li.First.Value);
 		}
+
+		[Test]
+		public void EqualityComparer ()
+		{
+			var list = new LinkedList<EquatableValue> ();
+			var mv  = new EquatableValue ("first");
+			list.AddFirst (mv);
+
+			var test = new EquatableValue ("FIRST");
+			Assert.IsTrue (list.Contains (test), "#1");
+			Assert.AreSame (mv, list.Find (test).Value, "#2");
+			Assert.AreSame (mv, list.FindLast (test).Value, "#3");
+		}
 	}
 }