GenericNull.java

class GenericNull {
    /**
     * In most type systems, null's type will be bottom and therefore the generic return type T will
     * be a supertype of null's type. However, in nullness and lock type systems, null's type is not
     * bottom, so they exclude this test. For the Lock Checker, null's type is bottom for
     * the @GuardedByUnknown hierarchy but not for the @LockPossiblyHeld hierarchy.
     */
    @SuppressWarnings({"nullness", "lock"})
    <T> T f() {
        return null;
    }
}