Bridge method resolution.

Foo.java

public abstract class Foo<T> {

    abstract void foo(T t);

    abstract T bar();

    public static void main(String[] args) {
        Foo<?> quxFoo = new Qux();
        Bar<?> quxBar = new Qux();

        Foo<?> barFoo = new Baz();
        Bar<?> barBaz = new Baz();

        quxFoo.foo(null);
        quxBar.foo(null); // does not bridge for foo(Number)

        barFoo.foo(null);
        barBaz.foo(null);

        quxFoo.bar();
        quxBar.bar();

        barFoo.bar();
        barBaz.bar();
    }
}

class Bar<S extends Number> extends Foo<S> {

    @Override
    void foo(S o) {
        System.out.println("bar");
    }

    @Override
    S bar() {
        System.out.println("bar");
        return null;
    }
}

class Qux extends Bar {

    @Override // parameter override considers erasure.
    void foo(Object o) {
        System.out.println("qux");
    }

    @Override
    Number bar() { // return type override considers upper bound.
        System.out.println("qux");
        return null;
    }
}

class Baz extends Bar<Integer> {

    @Override
    void foo(Integer o) {
        System.out.println("baz");
    }

    @Override
    Integer bar() {
        System.out.println("baz");
        return null;
    }
}