private
    fun sourceNamesFrom(entry: File): Sequence<String> =
        when {
            entry.isClassPathArchive -> sourceNamesFromJar(entry)
            entry.isDirectory -> sourceNamesFromDir(entry)
            else -> emptySequence()
        }

    private
    fun sourceNamesFromJar(jar: File): Sequence<String> =
        openJarFile(jar).run {
            entries().asSequence()