const_missing

# File activesupport/lib/active_support/dependencies.rb, line 175
      def const_missing(const_name, nesting = nil)
        klass_name = name.presence || "Object"

        unless nesting
          # We'll assume that the nesting of Foo::Bar is ["Foo::Bar", "Foo"]
          # even though it might not be, such as in the case of
          # class Foo::Bar; Baz; end
          nesting = []
          klass_name.to_s.scan(/::|$/) { nesting.unshift $` }
        end

        # If there are multiple levels of nesting to search under, the top
        # level is the one we want to report as the lookup fail.
        error = nil

        nesting.each do |namespace|
          begin
            return Dependencies.load_missing_constant Inflector.constantize(namespace), const_name
          rescue NoMethodError then raise
          rescue NameError => e
            error ||= e
          end
        end

        # Raise the first error for this set. If this const_missing came from an
        # earlier const_missing, this will result in the real error bubbling
        # all the way up
        raise error
      end