//x as Object
[object Test3]
//x as Test2
[object Test3]
//x as ITest2
[object Test3]
//x as Test3
[object Test3]
//x as ITest3
[object Test3]
//x as Test4
null
//y as Object
[object Test4]
//y as Test2
[object Test4]
//y as ITest2
[object Test4]
//y as Test3
[object Test4]
//y as ITest3
[object Test4]
//y as Test4
[object Test4]
