// CS4027: The awaiter type `A' must implement interface `System.Runtime.CompilerServices.INotifyCompletion' // Line: 33 using System.Threading.Tasks; static class S { public static A GetAwaiter (this int i) { return new A (); } } class A { bool IsCompleted { get { return true; } } public void OnCompleted (System.Action a) { } int GetResult () { return 3; } static async Task Test1 () { await 1; } }