Let's consider the base class:

package base;

public abstract class Base {
    protected enum BaseEnum {
        FIRST, SECOND, THIRD
    }
}

And its subclass:

package a;

import base.Base;

public class A {
    // The error message appears in case when NestedA is a nested or inner class
    protected /* static */ class InnerA extends Base {
        protected BaseEnum getEnumA() {
            return BaseEnum.FIRST;
        }

        protected int xxx() {
            BaseEnum enumA = getEnumA();
            switch (enumA) {
            // ^^ base.NestedBase.BaseEnum.values() is defined in an inaccessible class or interface
                case FIRST:
                case SECOND:
                    return 1;
                default:
                    return 2;
            }
        }

        protected int xxx2() {
            BaseEnum enumA = getEnumA();
            if (enumA == BaseEnum.FIRST || enumA == BaseEnum.SECOND) {
                return 1;
            } else {
                return 2;
            }
        }

        protected int xxx3() {
            System.out.println(BaseEnum.values());
            return 2;
        }
    }
}

When I am trying to compile it, a compilation error appears on line with switch statement in xxx() saying:

java: base.Base.BaseEnum.values() is defined in an inaccessible class or interface

Briefly the question is what exactly going on here? Why values() is even called here? If it is really called, why is it inaccessible? As you can see, I can properly access BaseEnum and its members from this class (see xxx2()) and even the values() method (which is public method of protected nested enum inside InnerA superclass, see xxx3()). Is access calculated as if this switch would be inside A class? If so, why?