LibJS: Disallow negative day lengths in ZonedDateTime.protoype.round

This is a normative change in the Temporal spec.

See: https://github.com/tc39/proposal-temporal/commit/6f04074

Userland/Libraries/LibJS/Runtime/ErrorTypes.h

@@ -273,7 +273,8 @@
     M(TemporalPropertyMustBeFinite, "Property must not be Infinity")                                                                    \
     M(TemporalPropertyMustBePositiveInteger, "Property must be a positive integer")                                                     \
     M(TemporalTimeZoneOffsetStringMismatch, "Time zone offset string mismatch: '{}' is not equal to '{}'")                              \
-    M(TemporalZonedDateTimeRoundZeroLengthDay, "Cannot round a ZonedDateTime in a calendar that has zero-length days")                  \
+    M(TemporalZonedDateTimeRoundZeroOrNegativeLengthDay, "Cannot round a ZonedDateTime in a calendar or time zone that has zero or "    \
+                                                         "negative length days")                                                        \
     M(ThisHasNotBeenInitialized, "|this| has not been initialized")                                                                     \
     M(ThisIsAlreadyInitialized, "|this| is already initialized")                                                                        \
     M(ToObjectNullOrUndefined, "ToObject on null or undefined")                                                                         \

Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp

@@ -1018,10 +1018,10 @@ JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::round)
     // 18. Let dayLengthNs be ℝ(endNs - startNs).
     auto day_length_ns = end_ns->big_integer().minus(start_ns.big_integer()).to_double();
 
-    // 19. If dayLengthNs is 0, then
-    if (day_length_ns == 0) {
+    // 19. If dayLengthNs ≤ 0, then
+    if (day_length_ns <= 0) {
         // a. Throw a RangeError exception.
-        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalZonedDateTimeRoundZeroLengthDay);
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalZonedDateTimeRoundZeroOrNegativeLengthDay);
     }
 
     // 20. Let roundResult be ! RoundISODateTime(temporalDateTime.[[ISOYear]], temporalDateTime.[[ISOMonth]], temporalDateTime.[[ISODay]], temporalDateTime.[[ISOHour]], temporalDateTime.[[ISOMinute]], temporalDateTime.[[ISOSecond]], temporalDateTime.[[ISOMillisecond]], temporalDateTime.[[ISOMicrosecond]], temporalDateTime.[[ISONanosecond]], roundingIncrement, smallestUnit, roundingMode, dayLengthNs).

Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.round.js

@@ -112,7 +112,35 @@ describe("errors", () => {
             zonedDateTime.round({ smallestUnit: "second" });
         }).toThrowWithMessage(
             RangeError,
-            "Cannot round a ZonedDateTime in a calendar that has zero-length days"
+            "Cannot round a ZonedDateTime in a calendar or time zone that has zero or negative length days"
+        );
+    });
+
+    test("time zone with negative length days", () => {
+        class CustomTimeZone extends Temporal.TimeZone {
+            constructor() {
+                super("UTC");
+                this.getPossibleInstantsForCallCount = 0;
+            }
+
+            getPossibleInstantsFor(temporalDateTime) {
+                this.getPossibleInstantsForCallCount++;
+
+                if (this.getPossibleInstantsForCallCount === 2) {
+                    return [new Temporal.Instant(-1n)];
+                }
+
+                return super.getPossibleInstantsFor(temporalDateTime);
+            }
+        }
+
+        const zonedDateTime = new Temporal.ZonedDateTime(1n, new CustomTimeZone());
+
+        expect(() => {
+            zonedDateTime.round({ smallestUnit: "second" });
+        }).toThrowWithMessage(
+            RangeError,
+            "Cannot round a ZonedDateTime in a calendar or time zone that has zero or negative length days"
         );
     });
 });