public HashSet(Collection<>) behaves differently on JDK 8 and JDK 11

[smillst]

        for (VariableElement field : new HashSet<>(fieldElts)) {
            field.toString(); // error with JDK 8, not JDK 11
        }

The above code issues an error with JDK 8, but not JDK 11. See the full test case below. I suspect it is because JDK 8 annotations are from classf iles, but JDK 11 annotations are from stub files.

import java.util.AbstractSet;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.VariableElement;

public class HashSetTest {

    void method(Set<VariableElement> fieldElts) {
        for (VariableElement field : new MySet<>(fieldElts)) {
            field.toString(); // ok with both JDK 8 and JDK 11
        }

        for (VariableElement field : new HashSet<>(fieldElts)) {
            field.toString(); // error with JDK 8, not JDK 11
        }
    }

    static class MySet<E> extends AbstractSet<E> {
        public MySet(Collection<? extends E> other) { }

        @Override
        public Iterator<E> iterator() {
            throw new RuntimeException();
        }

        @Override
        public int size() {
            return 0;
        }
    }
}

[smillst]

This no longer reproduces.