'x' is not interface

Sample code:

class x {
    //...
}
class c implements x {          // 'x' is not interface
    //...
}
interface i extends x {         // 'x' is not interface
    //...
}

You used symbol 'x' in the way that made Codenizer "think" that it should be interface (like some of the examples above). However 'x' is not interface.