in src/scanner.ts [761:775]
private isImplicitOctalLiteral(): boolean {
// Implicit octal, unless there is a non-octal digit.
// (Annex B.1.1 on Numeric Literals)
for (let i = this.index + 1; i < this.length; ++i) {
const ch = this.source[i];
if (ch === '8' || ch === '9') {
return false;
}
if (!Character.isOctalDigit(ch.charCodeAt(0))) {
return true;
}
}
return true;
}