There are some subtle behavioural differences between the Language Service and the regular compiler, for example: <a href="https:&#x2F;&#x2F;github.com&#x2F;Microsoft&#x2F;TypeScript&#x2F;issues&#x2F;5243" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;Microsoft&#x2F;TypeScript&#x2F;issues&#x2F;5243</a>