Visual Studio editor project (Assembly-CSharp-Editor) no longer recognizes types in non-editor scripts (Assembly-CSharp)

After upgrading to Unity 2020.2.0a9 and then downgrading to 2019.3.12f1 things got messed up in visual studio (both in visual studio 2019 & 2017 community edition). My editor scripts (in Assembly-CSharp-Editor) are no longer able to reference objects in regular scripts residing in Assembly-CSHarp.

The code still compiles fine in the unity editor, but not in visual studio. I no longer have access to intellisense and the visual studio is flooded with errors that makes it hard to work with.

What is going on?

Visual Studio Errors

@patrik-org This happened to me and several others who updated from versions prior to 2019.3.12f1. Downgrade to 2019.3.11f1 or 10f1 and see if that doesn’t fix your issues in Visual Studio. I believe 12f1 is the culprit.

I saw that the same question has been asked here:

So it looks like I’m not the only one encountering this issue.