Checks if an argument is variadic and also contains required tokens.

@example <arg...> >> true

@param val the value to inspect.
@param variadic the char representing variadic arguments.
function isArgVariadicRequired(val, variadic) {
    variadic = variadic || constants_1.VARIADIC_CHAR;
    return isArgRequired(val) && val.endsWith(variadic + '>');
}