Assertion check for TypeVariable.getUpperBound() fails

Documentation for method javax.lang.model.type.TypeVariable.getUpperBound() says that:

  * If it was declared with multiple upper bounds,
  * the result is an intersection type (modeled as a
  * {@link DeclaredType}).
  * Individual bounds can be found by examining the result's
  * {@linkplain Types#directSupertypes(TypeMirror) supertypes}.

It's not clear enough what the word "examining" means here, because direct supertypes also contain java.lang.Object. I would like to have possibility to compare results of supertypes examination with the results of TypeParameterElement.getBounds() method to check assertion above.

Please see examples below.

class MyClass<S extends List & Serializable> {
     void method(S s) { }
}

and processor for this source file:

import javax.annotation.processing.*;
import javax.lang.model.SourceVersion;
import javax.lang.model.type.*;
import javax.lang.model.util.ElementFilter;
import javax.lang.model.element.*;
import java.util.*;
import junit.framework.Assert;

@SupportedAnnotationTypes("*")
@SupportedSourceVersion(SourceVersion.RELEASE_6)
public class MyProcessor extends AbstractProcessor {

    private Set<? extends Element> rootElements;

    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        if (roundEnv.processingOver()) {
            performCheck();
        } else {
            rootElements = roundEnv.getRootElements();
        }
        return true;
    }

    private void performCheck() {
        TypeElement typeElement = (TypeElement) rootElements.iterator().next();
        ExecutableElement method = ElementFilter.methodsIn(typeElement.getEnclosedElements()).get(0);
        TypeVariable typeVariable = (TypeVariable) method.getParameters().get(0).asType();

        final TypeMirror upperBound = typeVariable.getUpperBound();

        TypeParameterElement typeParameterElement = ((TypeParameterElement) typeVariable.asElement());
        final List<? extends TypeMirror> bounds = typeParameterElement.getBounds();
        final HashSet actual = new HashSet<TypeMirror>(
                processingEnv.getTypeUtils().directSupertypes(upperBound));
        final HashSet expected = new HashSet<TypeMirror>(bounds);
        Assert.assertEquals("Sets of type mirrors are expected to be equal", expected, actual);
    }

}

Output will contain:

junit.framework.AssertionFailedError: Sets of type mirrors are expected to be equal expected:<[java.util.List, java.io.Serializable]> but was:<[java.lang.Object, java.util.List, java.io.Serializable]>