private List<PackageSymbol> getPackageInfoFiles(List<? extends JCCompilationUnit> units) {
        List<PackageSymbol> packages = List.nil();
        for (JCCompilationUnit unit : units) {
            if (isPkgInfo(unit.sourcefile, JavaFileObject.Kind.SOURCE)) {
                packages = packages.prepend(unit.packge);
            }
        }
        return packages.reverse();
    }