Temporal: Add coverage for BubbleRelativeDuration called with time unit

See: tc39/proposal-temporal#3121

A type assertion in the spec was incorrect, but the assertion wasn't hit
in the Firefox implementation in any test262 test. These three tests add
coverage for all the paths that would have hit that assertion.

test/built-ins/Temporal/Duration/prototype/round/bubble-time-unit.js

@@ -0,0 +1,83 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: Rounds relative to a date, bubbling up time units.
+info: |
+  https://github.com/tc39/proposal-temporal/issues/3121
+  Test case that calls BubbleRelativeDuration with a time unit as largestUnit.
+  This happens when time units round up and overflow a date unit, and
+  largestUnit is not "days" or higher, and the rounding is relative to a
+  PlainDateTime (ZonedDateTime would use Instant semantics in that case.)
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const relativeTo = new Temporal.PlainDate(2025, 6, 14);
+
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, /* hours = */ 14);
+  const result = duration.round({
+    relativeTo,
+    smallestUnit: "hours",
+    roundingIncrement: 12,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0);
+}
+
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 0, /* minutes = */ 1415);
+  const result = duration.round({
+    relativeTo,
+    smallestUnit: "minutes",
+    roundingIncrement: 30,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 1440, 0, 0, 0, 0);
+}
+
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 0, 0, /* seconds = */ 86375);
+  const result = duration.round({
+    relativeTo,
+    smallestUnit: "seconds",
+    roundingIncrement: 30,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 86400, 0, 0, 0);
+}
+
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 0, 0, 0, /* milliseconds = */ 86399_650);
+  const result = duration.round({
+    relativeTo,
+    smallestUnit: "milliseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 86400_000, 0, 0);
+}
+
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 0, 0, 0, 0, /* microseconds = */ 86399_999_650);
+  const result = duration.round({
+    relativeTo,
+    smallestUnit: "microseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 86400_000_000, 0);
+}
+
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 0, 0, 0, 0, 0, /* nanoseconds = */ 86399_999_999_650);
+  const result = duration.round({
+    relativeTo,
+    smallestUnit: "nanoseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 86400_000_000_000);
+}

test/built-ins/Temporal/PlainDateTime/prototype/since/bubble-time-unit.js

@@ -0,0 +1,83 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.since
+description: Rounds relative to a date, bubbling up time units.
+info: |
+  https://github.com/tc39/proposal-temporal/issues/3121
+  Test case that calls BubbleRelativeDuration with a time unit as largestUnit.
+  This happens when time units round up and overflow a date unit, and
+  largestUnit is not "days" or higher, and the rounding is relative to a
+  PlainDateTime (ZonedDateTime would use Instant semantics in that case.)
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainDateTime(2025, 6, 14);
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 14);
+  const result = later.since(earlier, {
+    largestUnit: "hours",
+    smallestUnit: "hours",
+    roundingIncrement: 12,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 35);
+  const result = later.since(earlier, {
+    largestUnit: "minutes",
+    smallestUnit: "minutes",
+    roundingIncrement: 30,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 1440, 0, 0, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 35);
+  const result = later.since(earlier, {
+    largestUnit: "seconds",
+    smallestUnit: "seconds",
+    roundingIncrement: 30,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 86400, 0, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 59, 650);
+  const result = later.since(earlier, {
+    largestUnit: "milliseconds",
+    smallestUnit: "milliseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 86400_000, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 59, 999, 650);
+  const result = later.since(earlier, {
+    largestUnit: "microseconds",
+    smallestUnit: "microseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 86400_000_000, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 59, 999, 999, 650);
+  const result = later.since(earlier, {
+    largestUnit: "nanoseconds",
+    smallestUnit: "nanoseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 86400_000_000_000);
+}

test/built-ins/Temporal/PlainDateTime/prototype/until/bubble-time-unit.js

@@ -0,0 +1,83 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.until
+description: Rounds relative to a date, bubbling up time units.
+info: |
+  https://github.com/tc39/proposal-temporal/issues/3121
+  Test case that calls BubbleRelativeDuration with a time unit as largestUnit.
+  This happens when time units round up and overflow a date unit, and
+  largestUnit is not "days" or higher, and the rounding is relative to a
+  PlainDateTime (ZonedDateTime would use Instant semantics in that case.)
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainDateTime(2025, 6, 14);
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 14);
+  const result = earlier.until(later, {
+    largestUnit: "hours",
+    smallestUnit: "hours",
+    roundingIncrement: 12,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 35);
+  const result = earlier.until(later, {
+    largestUnit: "minutes",
+    smallestUnit: "minutes",
+    roundingIncrement: 30,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 1440, 0, 0, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 35);
+  const result = earlier.until(later, {
+    largestUnit: "seconds",
+    smallestUnit: "seconds",
+    roundingIncrement: 30,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 86400, 0, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 59, 650);
+  const result = earlier.until(later, {
+    largestUnit: "milliseconds",
+    smallestUnit: "milliseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 86400_000, 0, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 59, 999, 650);
+  const result = earlier.until(later, {
+    largestUnit: "microseconds",
+    smallestUnit: "microseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 86400_000_000, 0);
+}
+
+{
+  const later = new Temporal.PlainDateTime(2025, 6, 14, 23, 59, 59, 999, 999, 650);
+  const result = earlier.until(later, {
+    largestUnit: "nanoseconds",
+    smallestUnit: "nanoseconds",
+    roundingIncrement: 500,
+    roundingMode: "ceil"
+  });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 86400_000_000_000);
+}