List<String> changes = filterChangesToReport(newClass, newInterfaces)
        if (changes.isEmpty()) {
            return null
        }
        return acceptOrReject(c, changes, Violation.error(c, " introduces internal or incubating interfaces"))
    }

    private Map<String, CtClass> collectImplementedInterfaces(CtClass c) {
        Map<String, CtClass> result = [:]
        collect(result, c)
        return result
    }