This never became a real language, but years ago Microsoft Research work on Project Midori, an attempt to make a managed programming language suitable for an operating, and the operating system to go with it. It was based off of C# and heavily modified. Joe Duffy at Microsoft Research wrote some good blogs on it, about approaches they took and why, problems they ran in to, etc.

https://joeduffyblog.com/2015/11/03/blogging-about-midori/