# File lib/sass/tree/visitors/perform.rb, line 299
  def visit_if(node)
    if node.expr.nil? || node.expr.perform(@environment).to_bool
      with_environment Sass::SemiGlobalEnvironment.new(@environment) do
        node.children.map {|c| visit(c)}
      end.flatten
    elsif node.else
      visit(node.else)
    else
      []
    end
  end