Angular cli可能并不总是支持最新版本的TypeScript. 存在一些与PR有关的问题:
-支持TypeScript 2.4+
- Typescript 2.4支持
- feat(@ angular/cli):支持TypeScript 2.4

Angular cli may not always support the latest version of TypeScript. There is some issues and PR's related to that:
- Support TypeScript 2.4+
- Typescript 2.4 support
- feat(@angular/cli): support TypeScript 2.4

也请记住，最新的TypeScript版本可能与您的Angular版本不兼容.

Also bare in mind that the latest TypeScript version might not be compatible with your Angular version.

如果您想跳转到新的/最新的TypeScript版本，后果自负.一旦这样做，您必须确保它不会破坏测试(ng t)，产品构建(ng build --prod)等之类的东西.

If you want to jump to a new/latest TypeScript version - it is at your own risk. Once you do so you have to make sure that it is not breaks anything like tests(ng t), prod build(ng build --prod), etc.

如果您坚持使用默认的cli TypeScript版本，那么-安全.

If you stick to the default cli TypeScript version you - are safe.

更新2017年9月9日:对于那些关心使用cli和最新TypeScript进行结帐的用户，此注释，因为最新的cli 1.4中引入了TypeScript version warning logic. 这是什么基于(cli团队推荐):

UPDATE 09 Sept 2017: For anyone who care about using the cli with the latest TypeScript checkout this recent github issue and this particular comment as there was a TypeScript version warning logic introduced in the latest cli 1.4. Here is what it is based on(angular cli team recommendation):

 const versionCombos = [
      { compiler: '>=2.3.1 <3.0.0', typescript: '>=2.0.2 <2.3.0' },
      { compiler: '>=4.0.0 <5.0.0', typescript: '>=2.1.0 <2.4.0' },
      { compiler: '>=5.0.0 <6.0.0', typescript: '>=2.4.0 <2.6.0' }
    ];