public static LazyTaskCompletionSource <T> Create() => new LazyTaskCompletionSource <T>(LazyTaskState <T> .Create());
public static LazyTaskCompletionSource <T> CreateConstant(T value) => new LazyTaskCompletionSource <T>(LazyTaskState <T> .CreateConstant(value));
private LazyTaskCompletionSource(LazyTaskState <T> state) { _state = state; _token = state.Version; }