You need to ensure that you have enlisted and built Roslyn sources with VS2017 tag on your machine. For further guidance, refer to the recipe, Setting up Roslyn enlistment in Chapter 8, Contribute Simple Functionality to Roslyn C# Compiler Open Source Code.
Additionally, the following four git commits on your enlistment to get the syntax definitions, parser support, binder support, and lowering support for the new operator and build CSharpCodeAnalysis project:
- https://github.com/mavasani/roslyn/commit/4b50f662c53e1b9fc83f81a819f29d11b85505d5
- https://github.com/mavasani/roslyn/commit/24144442e4faa9c54fe2a4b519455a1a45c29569
- https://github.com/mavasani/roslyn/commit/7a666595c8bf8d5e8c897540ec85ae3fa9fc5236
- https://github.com/mavasani/roslyn/commit/2c1ec4dc60ab0a64b7e9c01d1ec9a1fbcaa611da ...
