Constant Look-up


    class Foo
      A = 1
      B = 2
    end
    module Mod
      B = 3
      C = 4
      class Bar<Foo
        p Bar    # => Mod::Bar
        p A      # => 1
        p B      # => 3
        p C      # => 4
        p D      # => error! (by const_missing)
      end
    end