case ATTRIBUTE:
checker = new AttributeSpecifierChecker((AttributeSpecifier) specifier);
break;
case PSEUDO:
if (specifier instanceof PseudoClassSpecifier) {
checker = new PseudoClassSpecifierChecker((PseudoClassSpecifier) specifier);
} else if (specifier instanceof PseudoNthSpecifier) {
checker = new PseudoNthSpecifierChecker((PseudoNthSpecifier) specifier);
}
break;