Inline variable declaration not compiling

Question

I\'ve been getting a message in Visual Studio 2017, specifically, IDE0018 Variable declaration can be inlined.

So I try using an inline variable declara

Answer 1

I was able to resolve this by installing the Microsoft.Net.Compilers nuget package for v2.0.0-rc3, the only version installed prior was 1.3.2.

I still don't understand why the intellisense and compiler errors would show up if the installed compiler didn't support this.