Imported Upstream version 3.8.0

Former-commit-id: 6a76a29bd07d86e57c6c8da45c65ed5447d38a61

mcs/tests/gtest-618.cs

@@ -0,0 +1,73 @@
+using System;
+
+struct S1
+{
+	public static implicit operator int (S1? s)
+	{
+		return 1;
+	}
+}
+
+struct S2
+{
+	public static implicit operator int? (S2? s)
+	{
+		return null;
+	}
+}
+
+struct S3
+{
+	public static implicit operator int? (S3? s)
+	{
+		return 2;
+	}
+}
+
+struct S4
+{
+	public static implicit operator int? (S4 s)
+	{
+		return 3;
+	}
+}
+
+class C
+{
+	public static int Main ()
+	{
+		S1? s1 = new S1 ();
+		switch (s1) {
+		case 1:
+			break;
+		default:
+			return 1;
+		}
+
+		S2? s2 = new S2 ();
+		switch (s2) {
+		case null:
+			break;
+		default:
+			return 2;
+		}
+
+		S3? s3 = new S3 ();
+		switch (s3) {
+		case 2:
+			break;
+		default:
+			return 3;
+		}
+
+		S4 s4 = new S4 ();
+		switch (s4) {
+		case 3:
+			break;
+		default:
+			return 4;
+		}
+
+		return 0;
+	}
+}