{"ast_node_type":"variable","tokens":[{"end":61,"kind":"keyword","start":0,"text":"let"}]}
    let dir_path = file.parent().unwrap_or(&file).to_owned();
    // `MacroExpander::fully_expand_fragment` later restores, so "stack discipline" is maintained.
    cx.current_expansion.module = Rc::new(cx.current_expansion.module.with_dir_path(dir_path));