The type or namespace name `UnityStandardAssets' could not be found

Hi all

I got this strange bug:
CS0246: The type or namespace name `UnityStandardAssets’ could not be found. Are you missing a using directive or an assembly reference?

My scripts worked just fine before I accidentally added a new StandardAssets folder to my project as a subfolder separated from the original StandardAssets.

Deleting the new StandardAssets folder did not help. Restarting the Editor did not help. What else to do?
I can’t get anything done anymore due to this absurd bug.

I just deleted the original Standard Assets folder and imported the package again.
That ruined all the settings I had on the camera effects but at least it’s working now…

Restarting Unity3D solved the issue for me. Notice I found the solution here: https://forum.unity.com/threads/the-type-or-namespace-name-unitystandardassets-could-not-be-found.317921/