Module#parent is defined in introspection.rb as
parent_name = name.split('::')[0..-2] * '::'
parent_name.empty? ? Object : parent_name.constantize
And dependencies.rb defines Class#const_missing as
if [Object, Kernel].include?(self) || parent == self
If the || is not redundant there has to be a self different from
Object whose parent is himself, but I can't figure out an example.
Just to understand that line, is there any?