Imported Upstream version 3.6.0

Former-commit-id: da6be194a6b1221998fc28233f2503bd61dd9d14

mcs/tests/gtest-588.cs

@@ -0,0 +1,33 @@
+using System;
+
+struct S
+{
+	public static implicit operator short? (S s)
+	{
+		return 0;
+	}
+
+	public static implicit operator short (S s)
+	{
+		throw new ApplicationException ();
+	}
+}
+
+class Program
+{
+	public static int Main ()
+	{
+		S? s = null;
+		S? s2 = new S ();
+
+		long? i = s;
+		if (i != null)
+			return 1;
+
+		double? ui = s2;
+		if (ui == null)
+			return 2;
+
+		return 0;
+	}
+}