Never

src/UniTask.NetCore/Linq/Never.cs

@@ -0,0 +1,57 @@
+using System.Threading;
+
+namespace Cysharp.Threading.Tasks.Linq
+{
+    public static partial class UniTaskAsyncEnumerable
+    {
+        public static IUniTaskAsyncEnumerable<T> Never<T>()
+        {
+            return Cysharp.Threading.Tasks.Linq.Never<T>.Instance;
+        }
+    }
+
+    internal class Never<T> : IUniTaskAsyncEnumerable<T>
+    {
+        public static readonly IUniTaskAsyncEnumerable<T> Instance = new Never<T>();
+
+        Never()
+        {
+        }
+
+        public IUniTaskAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+            return new Enumerator(cancellationToken);
+        }
+
+        class Enumerator : IUniTaskAsyncEnumerator<T>
+        {
+            CancellationToken cancellationToken;
+
+            public Enumerator(CancellationToken cancellationToken)
+            {
+                this.cancellationToken = cancellationToken;
+            }
+
+            public T Current => default;
+
+            public UniTask<bool> MoveNextAsync()
+            {
+                var tcs = new UniTaskCompletionSource<bool>();
+
+                cancellationToken.Register(state =>
+                {
+                    var task = (UniTaskCompletionSource<bool>)state;
+                    task.TrySetCanceled(cancellationToken);
+                }, tcs);
+
+                return tcs.Task;
+            }
+
+            public UniTask DisposeAsync()
+            {
+                return default;
+            }
+        }
+    }
+}

src/UniTask.NetCoreTests/Linq/Factory.cs

@@ -59,6 +59,7 @@ namespace UniTask.NetCoreTests.Linq
             xs.Length.Should().Be(1);
             xs[0].Should().Be(value);
         }
+
     }