class Sass::Tree::PropNode

def check!
  if @options[:property_syntax] == :old && @prop_syntax == :new
    raise Sass::SyntaxError.new("Illegal property syntax: can't use new syntax when :property_syntax => :old is set.")
  elsif @options[:property_syntax] == :new && @prop_syntax == :old
    raise Sass::SyntaxError.new("Illegal property syntax: can't use old syntax when :property_syntax => :new is set.")
  elsif resolved_value.empty?
    raise Sass::SyntaxError.new("Invalid property: #{declaration.dump} (no value)." +
      pseudo_class_selector_message)
  end
end