snippet.rb

# An array of String subclasses does not sort using <=> on the subclass, WTF?

class StringSubclass < String
  def <=>(other)
    puts "using <=> in #{self.class}: #{caller.first}"
    super
  end
end

StringSubclass.new <=> StringSubclass.new
# => using <=> in StringSubclass: untitled:10

[StringSubclass.new, StringSubclass.new].sort
# => NOTHING!

# Let's try another built-in class.

class ArraySubclass < Array
  def <=>(other)
    puts "using <=> in #{self.class}: #{caller.first}"
    super
  end
end

ArraySubclass.new <=> ArraySubclass.new
# => using <=> in ArraySubclass: untitled:25

[ArraySubclass.new, ArraySubclass.new].sort
# => using <=> in ArraySubclass: untitled:28:in `sort'