Mongoid::Relations::Targets::Enumerable#last doesn't respect newly added documents when there are already persisted documents (no matter if enum loaded or not)

class Post

  include Mongoid::Document

  has_many :comments

end

class Comment

  include Mongoid::Document

  belongs_to :post

end

1.9.3p392 :006 >   p = Post.create

 => #<Post _id: 51b984bbf52876e795000001, >

1.9.3p392 :007 > p.comments.create

 => #<Comment _id: 51b984c2f52876e795000002, post_id: "51b984bbf52876e795000001">

1.9.3p392 :008 > p.comments.new

 => #<Comment _id: 51b984c7f52876e795000003, post_id: "51b984bbf52876e795000001">

1.9.3p392 :009 > p.comments.last

 => #<Comment _id: 51b984c2f52876e795000002,post_id: "51b984bbf52876e795000001">

1.9.3p392 :011 > p.comments.entries

 => [#<Comment _id: 51b984c2f52876e795000002,post_id: "51b984bbf52876e795000001">, #<Comment _id: 51b984c7f52876e795000003, post_id: "51b984bbf52876e795000001">]

1.9.3p392 :012 > p.comments._loaded?

 => true

1.9.3p392 :013 > p.comments.last

 => #<Comment _id: 51b984c2f52876e795000002, post_id: "51b984bbf52876e795000001">