AddDurationToOrSubtractDurationFromPlainYearMonth: CreateTemporalDate is fallible

[anba]

AddDurationToOrSubtractDurationFromPlainYearMonth, step 12.d:

Let endOfMonth be ! CreateTemporalDate(endOfMonthISO.[[Year]], endOfMonthISO.[[Month]], endOfMonthISO.[[Day]], calendar).

But CreateTemporalDate is fallible. Test case:

let cal = new class extends Temporal.Calendar {
  dateAdd(date, duration, options) {
    return new Temporal.PlainDate(-271821, 4, 19);
  }
}("iso8601");

let pym = new Temporal.PlainYearMonth(2000, 1, cal);

let d = Temporal.Duration.from({
  days: -1,
});

pym.add(d);

[ptomato]

Thanks! I concur.