The type or namespace name 'Foo' could not be found (when Foo exists in Project)

Unity Engine
1

Hi
In upgrading an older Unity project to 2018.4LTS created with 5.5 am getting a lot of the following errors in one class

The type or namespace name 'Foo' could not be found (are you missing a using directive or an assembly reference?)

But in this case the class Foo DOES exist in my Project and there is a ‘using’ directive. What else could possibly be causing this error?

2

Are you getting any other errors? Are you getting any errors inside your Foo class? Deleting the library and letting Unity rebuild it sometimes helps with this kind of problem, especially after an Editor upgrade (based on other threads similar to this I’ve seen over the years).