Missing calendar validation in ToRelativeTemporalObject and ToTemporalZonedDateTime

[anba]

ToRelativeTemporalObject, step 7.d. should probably be:

7.d. Set calendar to ? ToTemporalCalendarSlotValue(calendar, "iso8601").

Otherwise the calendar String value isn't validated to be a known, built-in calendar.

Also applies to ToTemporalZonedDateTime, step 6.j.

[justingrant]

Meeting 2023-04-13: This was a bug in the spec text of #2482 that wasn't caught before that PR was merged a few days ago, so we'll treat it as if it were a review comment on that PR and fix it now.

[ptomato]

I don't think we can use ToTemporalCalendarSlotValue here, because we should not accept all valid calendar string inputs as a value for a calendar annotation. For example, this proposed change would make the following code work:

Temporal.ZonedDateTime.from('2023-04-13T00[UTC][u-ca=2023-04-13]')

I think we can use IsBuiltinCalendar here instead, because result.[[Calendar]] should already be an identifier — we just need to make sure it's a known builtin one.

According to the current spec text, this already works for the other types, e.g.:

Temporal.PlainDate.from('2023-04-13[u-ca=2023-04-13]')

This is also a regression from #2482. So, the bug that needs to be fixed here is slightly more extensive than originally reported, but still doable.

[ptomato]

(The time zone annotation doesn't have this problem because an ISO string isn't a syntactically valid time zone identifier.)