我是 Angular 4 的新手，正在尝试弄清一个简单项目的基本结构。我已经测试了我的项目，昨天运行良好。但是今天当我打开我的项目并想要执行“ng serve”时，它显示以下错误。不知道问题是什么。

TypeError: Cannot read property 'length' of undefined
at createSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:15457:109)
at parseSourceFileWorker (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:15389:26)
at Object.parseSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:15338:26)
at Object.createSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:15192:29)
at VirtualFileStats.getSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\@ngtools\webpack\src\compiler_host.js:66:35)
at WebpackCompilerHost.getSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\@ngtools\webpack\src\compiler_host.js:213:38)
at findSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:67909:29)
at processImportedModules (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:68056:25)
at findSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:67937:17)
at processSourceFile (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:67840:27)
at processRootFile (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:67728:13)
at C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:67018:60
at Object.forEach (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:1449:30)
at Object.createProgram (C:\Users\IR\Desktop\angular-first-project\node_modules\typescript\lib\typescript.js:67018:16)
at AotPlugin._setupOptions (C:\Users\IR\Desktop\angular-first-project\node_modules\@ngtools\webpack\src\plugin.js:129:28)
at new AotPlugin (C:\Users\IR\Desktop\angular-first-project\node_modules\@ngtools\webpack\src\plugin.js:26:14)

提前致谢。