/**
 * Links sometimes, though not always, benefit from `title` attributes. Links
 * without are never invalid but it’s a good idea to check.
 */
a:empty:not([title]) {
  @include warning("`title` attribute required if empty");
}

// Double-check any links whose `href` is empty or something questionable.
// Use <button> instead
a:not([href]),
a[href=""],
a[href="#"],
a[href^="javascript"] {
  @include warning("Use <button> instead of link");
}