Set::SubclassCompatible#<=>

# File tmp/rubies/ruby-4.0.0/lib/set/subclass_compatible.rb, line 161
def <=>(set)
  return unless set.is_a?(Set)

  case size <=> set.size
  when -1 then -1 if proper_subset?(set)
  when +1 then +1 if proper_superset?(set)
  else 0 if self.==(set)
  end
end