Refactor WithCancellationToken to separate file.

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

@@ -0,0 +1,63 @@
+// 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;
+using System.Threading.Tasks;
+
+namespace System.Linq
+{
+    public static partial class AsyncEnumerable
+    {
+        // REVIEW: [LDM-2018-11-28] Should return type be a struct or just the interface type? Should this live in the System.Linq namespace or in System.Collections.Generic?
+
+        public static WithCancellationTokenAsyncEnumerable<T> WithCancellationToken<T>(this IAsyncEnumerable<T> source, CancellationToken cancellationToken)
+        {
+            if (source == null)
+                throw Error.ArgumentNull(nameof(source));
+
+            return new WithCancellationTokenAsyncEnumerable<T>(source, cancellationToken);
+        }
+
+        // REVIEW: Explicit implementation of the interfaces allows for composition with other "modifier operators" such as ConfigureAwait.
+        //         We expect that the "await foreach" statement will bind to the public struct methods, thus avoiding boxing.
+
+        public readonly struct WithCancellationTokenAsyncEnumerable<T> : IAsyncEnumerable<T>
+        {
+            private readonly IAsyncEnumerable<T> _source;
+            private readonly CancellationToken _cancellationToken;
+
+            public WithCancellationTokenAsyncEnumerable(IAsyncEnumerable<T> source, CancellationToken cancellationToken)
+            {
+                _source = source;
+                _cancellationToken = cancellationToken;
+            }
+
+            // REVIEW: Should we simply ignore the second cancellation token or should we link the two?
+            // REVIEW: [LDM-2018-11-28] Should we have eager cancellation here too?
+
+            public WithCancellationAsyncEnumerator GetAsyncEnumerator(CancellationToken cancellationToken)
+                => new WithCancellationAsyncEnumerator(_source.GetAsyncEnumerator(_cancellationToken));
+
+            IAsyncEnumerator<T> IAsyncEnumerable<T>.GetAsyncEnumerator(CancellationToken cancellationToken)
+                => GetAsyncEnumerator(cancellationToken);
+
+            public readonly struct WithCancellationAsyncEnumerator : IAsyncEnumerator<T>
+            {
+                private readonly IAsyncEnumerator<T> _enumerator;
+
+                public WithCancellationAsyncEnumerator(IAsyncEnumerator<T> enumerator)
+                {
+                    _enumerator = enumerator;
+                }
+
+                public T Current => _enumerator.Current;
+
+                public ValueTask DisposeAsync() => _enumerator.DisposeAsync();
+
+                public ValueTask<bool> MoveNextAsync() => _enumerator.MoveNextAsync();
+            }
+        }
+    }
+}

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

@@ -19,16 +19,6 @@ namespace System.Linq
             return new AnonymousAsyncEnumerable<T>(getEnumerator);
         }
 
-        // REVIEW: [LDM-2018-11-28] Should return type be a struct or just the interface type?
-
-        public static WithCancellationTokenAsyncEnumerable<T> WithCancellationToken<T>(this IAsyncEnumerable<T> source, CancellationToken cancellationToken)
-        {
-            if (source == null)
-                throw Error.ArgumentNull(nameof(source));
-
-            return new WithCancellationTokenAsyncEnumerable<T>(source, cancellationToken);
-        }
-
         private sealed class AnonymousAsyncEnumerable<T> : IAsyncEnumerable<T>
         {
             private readonly Func<CancellationToken, IAsyncEnumerator<T>> _getEnumerator;
@@ -47,45 +37,5 @@ namespace System.Linq
                 return _getEnumerator(cancellationToken);
             }
         }
-
-        // REVIEW: Explicit implementation of the interfaces allows for composition with other "modifier operators" such as ConfigureAwait.
-        //         We expect that the "await foreach" statement will bind to the public struct methods, thus avoiding boxing.
-
-        public readonly struct WithCancellationTokenAsyncEnumerable<T> : IAsyncEnumerable<T>
-        {
-            private readonly IAsyncEnumerable<T> _source;
-            private readonly CancellationToken _cancellationToken;
-
-            public WithCancellationTokenAsyncEnumerable(IAsyncEnumerable<T> source, CancellationToken cancellationToken)
-            {
-                _source = source;
-                _cancellationToken = cancellationToken;
-            }
-
-            // REVIEW: Should we simply ignore the second cancellation token or should we link the two?
-            // REVIEW: [LDM-2018-11-28] Should we have eager cancellation here too?
-
-            public WithCancellationAsyncEnumerator GetAsyncEnumerator(CancellationToken cancellationToken)
-                => new WithCancellationAsyncEnumerator(_source.GetAsyncEnumerator(_cancellationToken));
-
-            IAsyncEnumerator<T> IAsyncEnumerable<T>.GetAsyncEnumerator(CancellationToken cancellationToken)
-                => GetAsyncEnumerator(cancellationToken);
-
-            public readonly struct WithCancellationAsyncEnumerator : IAsyncEnumerator<T>
-            {
-                private readonly IAsyncEnumerator<T> _enumerator;
-
-                public WithCancellationAsyncEnumerator(IAsyncEnumerator<T> enumerator)
-                {
-                    _enumerator = enumerator;
-                }
-
-                public T Current => _enumerator.Current;
-
-                public ValueTask DisposeAsync() => _enumerator.DisposeAsync();
-
-                public ValueTask<bool> MoveNextAsync() => _enumerator.MoveNextAsync();
-            }
-        }
     }
 }