class DestroyTest {
    public sprite:Phaser.Sprite;

    public test():void {
        if(this.sprite != undefined){
            this.sprite.destroy();
        }

        var bitmapData: Phaser.BitmapData = game.make.bitmapData(50, 50);
        this.sprite = new Phaser.Sprite(game, 0,0, bitmapData);
    }
}
// This block is what causes this.sprite.destroy(); to be removed from the top class
class OtherClass {
    public destroy():void {}
}
// =======================
var game = new Phaser.Game(
    50,
    50,
    Phaser.AUTO,
    'phaser-game',
    {
        create: function(){
            var destroyTest:DestroyTest = new DestroyTest();
            destroyTest.test();
        }
    }
);