using System.Reactive.Disposables; using System.Runtime.CompilerServices; namespace System.Reactive.Linq.ObservableImpl { [NullableContext(1)] [Nullable(0)] internal sealed class Never<[Nullable(2)] TResult> : IObservable<TResult> { internal static readonly IObservable<TResult> Default = new System.Reactive.Linq.ObservableImpl.Never<TResult>(); private Never() { } public IDisposable Subscribe(IObserver<TResult> observer) { if (observer == null) throw new ArgumentNullException("observer"); return Disposable.Empty; } } }