Laravel 5.4 存储：下载文件.文件不存在，但显然存在

我一直在为这件事转来转go .我有上传工作与以下工作:

public function store(Tool $tool)
{

     If(Input::hasFile('file')){
        $file = Input::file('file');
        $name = $file->getClientOriginalName();
        $path=Storage::put('public',$file);         //Storage::disk('local')->put($name,$file,'public');

        $file = new File;
        $file->tool_id = $tool->id;
        $file->file_name = $name;
        $file->path_to_file = $path;
        $file->name_on_disk = basename($path);
        $file->user_name = \Auth::user()->name;
        $file->save();

        return back();
    }

但是，当我try 下载时:

public function show($filename)
    {   

        $url = Storage::disk('public')->url($filename);

        ///$file = Storage::disk('public')->get($filename);
        return response()->download($url);
    }

我从laravel那里得到了FileNotFound异常

$file = Storage::disk('public')->get($filename);
return response()->download($file);

我明白了

FileNotFoundException in File.php line 37: The file "use calib;

插入

这就是文件的实际内容...

它显然能找到文件.但为什么不下载呢？