public class AAA : Object {
	public string str { get; set; default = ""; }
}

void func (string str)
{
}

void main () {
	string tmp = "aaa";
	string n = null;
	tmp = tmp.concat (n, "B");
	print (tmp);

	print ("\n---- AAA ----\n");
	var a = new AAA ();
	print ("AAA".concat(a.str, "BBB"));

	var tmp2 = "";//null;
	func (tmp2);

	print ("\n---- Construct ----\n");
	var tmp3 = Object.new (typeof (AAA)) as AAA;
	print ("AAA".concat(tmp3.str, "BBB"));
}