Imported Upstream version 3.10.0

Former-commit-id: 172c8e3c300b39d5785c7a3e8dfb08ebdbc1a99b

mcs/tests/test-903.cs

@@ -0,0 +1,22 @@
+using System;
+
+struct S
+{
+}
+
+class C
+{
+	public static implicit operator S (C c)
+	{
+		return new S ();
+	}
+}
+
+class Program
+{
+	static void Main ()
+	{
+		C c = new C ();
+		var x = c ?? new S ();
+	}
+}