Throwing exception in constructor

[Stijn Herreman]

Why is the return statement required, while nothing after the Exception 
is executed?
Error: one path skips constructor
        public this(string p1, string p2, string p3)
        {
                string json = download_string(...);
                
                if (json is null)
                {
                        throw new Exception("404");
                        writeln("test");
                        return;
                }
                else
                {
                        this(json);
                }
        }
        
        package this(string json)
        {
                ...
        }