Moving Empty to its own file.

Ix.NET/Source/System.Linq.Async/System/Linq/AsyncEnumerable.cs

@@ -17,11 +17,6 @@ namespace System.Linq
             return source.Select(x => x);
         }
 
-        public static IAsyncEnumerable<TValue> Empty<TValue>()
-        {
-            return CreateEnumerable(() => CreateEnumerator<TValue>(ct => TaskExt.False, current: null, dispose: null));
-        }
-
         public static IAsyncEnumerable<TValue> Return<TValue>(TValue value)
         {
             return new[] { value }.ToAsyncEnumerable();

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/Empty.cs

@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information. 
+
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace System.Linq
+{
+    public static partial class AsyncEnumerable
+    {
+        public static IAsyncEnumerable<TValue> Empty<TValue>()
+        {
+            return CreateEnumerable(() => CreateEnumerator<TValue>(ct => TaskExt.False, current: null, dispose: null));
+        }
+    }
+}