Imported Upstream version 3.12.0

Former-commit-id: cf92446697332992ec36726e78eb8703e1f259d7

mcs/tests/test-903.cs

@@ -6,17 +6,36 @@ struct S
 
 class C
 {
+	public static int ConversionCalled;
+
 	public static implicit operator S (C c)
 	{
+		++ConversionCalled;
 		return new S ();
 	}
 }
 
 class Program
 {
-	static void Main ()
+	static C field;
+
+	static int Main ()
 	{
 		C c = new C ();
 		var x = c ?? new S ();
+
+		if (C.ConversionCalled != 1)
+			return 1;
+
+		c = null;
+		x = c ?? new S ();
+		if (C.ConversionCalled != 1)
+			return 2;
+
+		x = field ?? new S ();
+		if (C.ConversionCalled != 1)
+			return 3;
+
+		return 0;
 	}
 }