Understanding “create_association” and invalid objects

The documentation on the “create_association” method of the “belongs_to” association reads:

create_association(attributes = {}) Returns a new object of the associated type that has been instantiated with attributes, linked to this object through a foreign key, and that has already been saved (if it passed the validation).*

My expectation from this documentation is that calling “object.create_association” will return the newly created object if both objects save successfully and “false” if either object fails to save (due to failed validations, for example); or throw an error.

My experience, however, is that “create_association” returns the newly created object regardless of whether it saved successfully or not.

How can I catch and handle a situation where “create_association” instantiates and links a new object but is unable to save it?

Rails 2.3.5

I think that "and that has already been saved (if it passed the validation)" means only that the new object will only be saved if it passed the validations, not that it won't be instantiated in either case.

the new object will only be saved if it passed the validations, not that it won't be instantiated in either case.

How can I catch and handle a situation where this occurs (the new object is instantiated, but not saved)?