ensure_not_nested

# File activerecord/lib/active_record/associations/through_association.rb, line 84
        def ensure_not_nested
          if reflection.nested?
            if reflection.has_one?
              raise HasOneThroughNestedAssociationsAreReadonly.new(owner, reflection)
            else
              raise HasManyThroughNestedAssociationsAreReadonly.new(owner, reflection)
            end
          end
        end