Callback type which allows either one Dynamic arg, or no args

callback.hx

abstract Callback(Dynamic->Void) from Dynamic->Void {
	inline function new(f)
		this = f;
		
	public inline function invoke(data:Dynamic):Void
		(this)(data);
		
	@:from static function fromNiladic(f:Void->Void):Callback
		return new Callback(function (x) f());
}