association_valid?

# File activerecord/lib/active_record/autosave_association.rb, line 278
    def association_valid?(reflection, association)
      return true if association.destroyed? || association.marked_for_destruction?

      unless valid = association.valid?
        if reflection.options[:autosave]
          association.errors.each_error do |attribute, error|
            attribute = "#{reflection.name}.#{attribute}"
            errors.add(attribute, error.dup) unless errors.on(attribute)
          end
        else
          errors.add(reflection.name)
        end
      end
      valid
    end