I propose the following addition to section 8.1:
"If the set of decorated types of a decorator is empty, the container automatically detects the problem and treats it as a definition error."

This would be helpful in cases where the developer is not aware that a decorator and decorated bean must share the same interface, and thinks that a decorator can be defined simply by extending the decorated class (as in the following example).

public class MyBean {
    public Object foo() {...}
}

@Decorator
public class MyDecorator extends MyBean {
    @Inject @Delegate MyBean delegate;
    public Object foo() {...}
}

Even though the spec does explicitly state that "superclasses are not decorated types of the decorator", throwing an error would probably save some people's debugging time.