I got a compile error just after updating to 2.80. Here’s a screenshot. I’m using Unity 2017.3.1p3 on Windows 10. Any idea?
Also, do you have a changelog? I’d like to know what changed from 2.64 to 2.80.
Whenever you update, it is preferable to please completely delete the previous installation folder and only then import the new version package anew. This will avoid any possible compile errors like this one 🙂
The change log of all versions can be seen in the following link: