In debug mode, Visual Studio recommended the following syntax change for null coalescing but then complains that this syntax requires at least C# 8.0.
However this is a dotnet 5.0 project specifically targeting C#9.0 on a supported VS2019 build:
So it seems like something is being cached to make this an issue but the basics (clean solution, reboot, vs update, etc) don't seem to clear the issue. Weirdly it works fine in release mode. How to shake this error out?