public void validateAnnotation(JCAnnotation a, Symbol s) {
        validateAnnotationTree(a);

        if (!annotationApplicable(a, s))
            log.error(a.pos(), "annotation.type.not.applicable");

        if (a.annotationType.type.tsym == syms.overrideType.tsym) {
            if (!isOverrider(s))
                log.error(a.pos(), "method.does.not.override.superclass");
        }
    }