// Forms require `action` attributes
form:not([action]) {
  @include error("`action` attribute required");
}

// input`s need `type` attributes
input:not([type]) {
  @include error("`type` attribute required");
}

// textarea`s need `rows` and `cols` attributes
textarea:not([rows]),
textarea:not([cols]) {
  @include error("`rows` & `cols` attributes required");
}

// submit buttons need a `value` attribute
input[type="submit"]:not([value]) {
  @include error("`value` attribute required");
}