Fluent (?) interface trick for Haxe.

Main.hx

using Main.Smartxin;

class A {
	public var width:Int;
	public function new() { }
}

class B extends A {
	public var height:Int;
	public function new() super();
}

class Main {
	static function main() {
		var b = new B();
		inline function traceB() trace(b.width + "x" + b.height);
		//
		b.setWidth(4).setHeight(8);
		traceB();
		b.setSize(5, 3);
		traceB();
		b.setSize2(7, 8);
		traceB();
	}
}

class Smartxin {
	public static function setWidth<T:A>(self:T, value:Int):T {
		self.width = value;
		return self;
	}
	
	public static function setHeight<T:B>(self:T, value:Int):T {
		self.height = value;
		return self;
	}
	
	public static function setSize<T:B>(self:T, width:Int, height:Int):T {
		self.width = width;
		self.height = height;
		return self;
	}
	
	public static function setSize2<T:B>(self:T, width:Int, height:Int):T {
		return self.setWidth(width).setHeight(height);
	}
}