The goal is to prevent assignment of temporary or evaluated meshes to objects from the main database. Majority of the change is actually related on passing reports around. On a positive side there are more error prints which can become more visible to scripters. There are still possible further improvements in the related areas. For example, disable user counting for evaluated ID datablocks when assignment happens. But can also happen later on as a separate improvement. Reviewers: brecht, campbellbarton, mont29 Reviewed By: brecht Differential Revision: https://developer.blender.org/D4884