polyfill: rounding large duration to days causes 1 day error

[fabon-f]

// expected value is P100017D, but the reference polyfill returns P100016D
Temporal.Duration.from('P100016DT0.0000001S').round({ smallestUnit: 'day', roundingMode: 'ceil' });

SpiderMonkey and V8 returns P100017D, but the reference polyfill returns P100016D. I believe SM and V8 is spec-compliant, but perhaps I'm wrong.

[ptomato]

Yes, that looks like it should be rounding up to 100017 days! This is probably a polyfill bug, but we should double-check the spec just in case. And once we find the bug it likely requires a test262 test.

[fabon-f]

I think this line is the culprit because it causes floating-point precision loss. The spec uses a mathematical value here, so the spec seems OK, but a note for implementers would be nice-to-have.

proposal-temporal/polyfill/lib/duration.mjs

Line 293 in 9291822

let days = internalDuration.date.days + quotient + ES.TotalTimeDuration(remainder, 'day');