Imported Upstream version 4.3.2.467

Former-commit-id: 9c2cb47f45fa221e661ab616387c9cda183f283d

mcs/tests/test-931.cs

@@ -0,0 +1,20 @@
+using System;
+
+class MainClass
+{
+	public static implicit operator string (MainClass src)
+	{
+		return null;
+	}
+
+	public static int Main ()
+	{
+		var obj = new MainClass ();
+		var s = "x";
+		var res = (string) obj ?? s;
+		if (res != "x")
+			return 1;
+
+		return 0;
+	}
+}