class Sass::Tree::PropNode

def pseudo_class_selector_message
  if @prop_syntax == :new ||
      custom_property? ||
      !value.first.is_a?(Sass::Script::Tree::Literal) ||
      !value.first.value.is_a?(Sass::Script::Value::String) ||
      !value.first.value.value.empty?
    return ""
  end
  "\nIf #{declaration.dump} should be a selector, use \"\\#{declaration}\" instead."
end