Follow up from change 49c2427, copying the comment from the Java implementation to the C++ impl.
void AsYouTypeFormatter::InputDigitHelper(char next_char, string* number) {
DCHECK(number);
number->clear();
+ // Note that formattingTemplate is not guaranteed to have a value, it could be
+ // empty, e.g. when the next digit is entered after extracting an IDD or NDD.
const char32 placeholder_codepoint = UnicodeString(kDigitPlaceholder)[0];
int placeholder_pos = formatting_template_
.tempSubString(last_match_position_).indexOf(placeholder_codepoint);
i18n.phonenumbers.AsYouTypeFormatter.prototype.inputDigitHelper_ =
function(nextChar) {
+ // Note that formattingTemplate is not guaranteed to have a value, it could be
+ // empty, e.g. when the next digit is entered after extracting an IDD or NDD.
/** @type {string} */
var formattingTemplate = this.formattingTemplate_.toString();
if (formattingTemplate.substring(this.lastMatchPosition_)