Imported Upstream version 3.6.0

Former-commit-id: da6be194a6b1221998fc28233f2503bd61dd9d14

mcs/tests/test-623.cs

@@ -0,0 +1,23 @@
+//
+// fixed
+//
+interface I {
+	void a ();
+}
+
+abstract class X : I {
+	public abstract void a ();
+}
+
+class Y : X {
+	override public void a () {
+		System.Console.WriteLine ("Hello!");
+		return;
+	}
+
+	public static void Main () {
+		Y y = new Y ();
+
+		((I) y ).a ();
+	}
+}