String array access upon a typedef from a JSON in Haxe

package ;
import haxe.Json;

abstract StringKey({}) from {} {
    @:extern @:arrayAccess public inline function arrayAccess(key:String):Dynamic {
        return Reflect.field(this, key);
    }
    @:extern @:arrayAccess public inline function arrayWrite<T>(key:String, value:T):T {
        Reflect.setField(this, key, value);
        return value;
    }
}

typedef Some = {
    sk: StringKey,
}

class Main {

    static function main() {
        var aVal:Int = Std.int(Math.random() * 9 + 1);
        var a:Some = Json.parse("{ \"sk\": { \"a\": " + aVal + ", \"b\": 3 } }");
        trace(a);
        trace(a.sk["a"]);
    }

}