angular编译出错解决办法Angular Compiler was detected but it was an instance of the wrong class.

出现如下错误：

错误信息

Module build failed: Error: Angular Compiler was detected but it was an instance of the wrong class.
This likely means you have several @ngtools/webpack packages installed. You can check this with `npm ls @ngtools/webpack`, and then remove the extra copies.

大致意思是，出现错误，原因可能是安装了几个不同版本的@ngtools/webpack包，你可以使用npm ls @ngtools/webpack命令来检查，然后删除多余的副本。

npm ls @ngtools/webpack

果然有两个版本

提示@ngtools/webpack@1.8.0版本是多于的，然后去目录下面把它删掉，问题解决。