scope-wtf.rb

module Foo
  class Error < StandardError; end
end

module Foo
  class Baz
    def initialize
      puts Error
    end
  end
end

class Foo::Bar
  def initialize
    puts Error
  end
end

# Works:
puts Foo::Baz.new

# Fails: uninitialized constant Foo::Bar::Error
puts Foo::Bar.new

Sorry but that's not obvious, a lot of people think the second construct is a shortcut for the first. Including me-five-minutes-ago. Principle of least surprise anyone ?