link_to_ifにブロック渡した時の挙動が欲しいのと違う ref: http://qiita.com/ppworks/items/9bf917edf0d4927b15bd

application_helper.rb

module ApplicationHelper
  def link_to_if_with_block(condition, options = nil, html_options = nil, &block)
    if condition
      link_to(options, html_options, &block)
    else
      capture(&block)
    end
  end
end

hoge.html.haml

= link_to_if_with_block user_signed_in? user_path(current_user) do
  .image
    = user.image
  .name
    = user.name