docs: @Requires({
      "files != null",
      "diagnostics != null"
    })
    @Ensures("result != null")
    public CompilationTask getTask(List<? extends JavaFileObject> files,
        DiagnosticListener<JavaFileObject> diagnostics) {
      return javaCompiler.getTask(null, fileManager, diagnostics,
                                  OPTIONS, null, files);
    }