generalization

src/generator/future/Future.java

@@ -4,19 +4,23 @@ public interface Future<R> {
 
     @SuppressWarnings("unchecked")
     default R poll(Waker waker){
-        return (R) Pending.INSTANCE;
+        return (R)Pending.INSTANCE;
     }
 
     default R await(){
-        throw new RuntimeException();
+        throw new RuntimeException("NO!");
     }
 
     static <R> Future<R> ret(R r){
-        throw new RuntimeException();
+        throw new RuntimeException("NO!");
+    }
+
+    static void yield() {
+        throw new RuntimeException("NO!");
     }
 
     final class Pending{
-        private static final Pending INSTANCE = new Pending();
+        public static final Pending INSTANCE = new Pending();
         private Pending(){}
     }
 }