Implement to_ary to avoid calls to method_missing

[tenderlove]

The following code is calls method missing and emits annoying warnings when -d is used:

class Item
  def method_missing(name, *args)
    p "method_missing(#{name})"
    super
  end
end

p [[Item.new]].flatten

We can silence these warnings by implementing a to_ary that returns nil:

class Item
  def method_missing(name, *args)
    p "method_missing(#{name})"
    super
  end

  private
  def to_ary
    nil
  end
end

p [[Item.new]].flatten

According to ruby spec it's OK for to_ary to return nil, and it will just be ignored. We can also see that the ruby implementation agrees.

This patch adds to_ary for two reasons:

• Avoiding expensive calls to method_missing
• Silencing warnings when -d is enabled.

Thanks!