Unexpected compilation error Enum<Enum<...

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.util.Set;
import java.util.TreeSet;

public class Test<K extends Enum<K>, A extends Annotation> {

    public static <K extends Enum<K>, A extends Annotation> Set<String> foo(Test<K, A> test, Class<?> cl){
        Set<String> result = new TreeSet<>();
        for (Field field : cl.getFields()) {
            result.addAll(foo(test, field.getType()));
        }
        return result;
    }
}

Produce error
Error:(13, 30) java: [type.argument.type.incompatible] incompatible types in type argument.
found : Enum<K extends Enum>
required: Enum<Enum<K extends Enum>>

CF 2.1.0

Start by compiling the supplied Java reproducer with Checker Framework 2.1.0 and inspect the type-argument incompatibility reported at line 13. Trace the checker’s handling of the nested Enum and Annotation bounds; done means the valid case no longer produces the diagnostic, with a regression test covering the reproducer.