code: private void setClassPath() throws IOException {
      String fullPath = file.getAbsolutePath();
      String rootPath = fullPath.substring(0, fullPath.lastIndexOf(classFile.getRelativePath()));
      List<File> classPath = new ArrayList<>();
      classPath.add(new File(rootPath));
      parserEnv.fileManager().setLocation(StandardLocation.CLASS_PATH, classPath);
    }
docs: Set classpath to the root path of the input file, to support typeElement lookup.