Using abstract to creating immutable objects in Haxe

Immutable.hx

class Foo {
   public function new( val ) x = val;
   public var x : Int;
}


abstract ConstFoo(Foo) from Foo {
  public var x(get, never) : Int;
  function get_x() return this.x;
}

class Test {
    static function main() {
        var foo = new Foo(41);
        foo.x = 42;
        trace(foo.x); // 42
        
        var const_foo :ConstFoo = foo;
        //const_foo.x = 43; // error        
        trace(const_foo.x); // 42
        
		    // *Can* still be bypassed
        (cast const_foo).x = 123;
        trace(const_foo.x); // 123
    }
}