LibJS: Add sign(Crypto::SignedBigInteger const&) overload

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

@@ -952,6 +952,20 @@ double sign(double n)
     return 1;
 }
 
+double sign(Crypto::SignedBigInteger const& n)
+{
+    // 1. If n is NaN, n is +0𝔽, or n is −0𝔽, return n.
+    if (n == Crypto::SignedBigInteger { 0 })
+        return n.is_negative() ? -0 : 0;
+
+    // 2. If n < +0𝔽, return −1𝔽.
+    if (n.is_negative())
+        return -1;
+
+    // 3. Return 1𝔽.
+    return 1;
+}
+
 // 13.29 ConstrainToRange ( x, minimum, maximum ), https://tc39.es/proposal-temporal/#sec-temporal-constraintorange
 double constrain_to_range(double x, double minimum, double maximum)
 {

Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h

@@ -124,6 +124,7 @@ Optional<u16> maximum_temporal_duration_rounding_increment(StringView unit);
 ThrowCompletionOr<void> reject_object_with_calendar_or_time_zone(GlobalObject&, Object&);
 String format_seconds_string_part(u8 second, u16 millisecond, u16 microsecond, u16 nanosecond, Variant<StringView, u8> const& precision);
 double sign(double);
+double sign(Crypto::SignedBigInteger const&);
 double constrain_to_range(double x, double minimum, double maximum);
 i64 round_number_to_increment(double, u64 increment, StringView rounding_mode);
 BigInt* round_number_to_increment(GlobalObject&, BigInt const&, u64 increment, StringView rounding_mode);

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

@@ -403,13 +403,7 @@ ThrowCompletionOr<NanosecondsToDaysResult> nanoseconds_to_days(GlobalObject& glo
     auto nanoseconds = nanoseconds_bigint.big_integer();
 
     // 3. Let sign be ! ℝ(Sign(𝔽(nanoseconds))).
-    i8 sign;
-    if (nanoseconds == Crypto::UnsignedBigInteger { 0 })
-        sign = 0;
-    else if (nanoseconds.is_negative())
-        sign = -1;
-    else
-        sign = 1;
+    auto sign = Temporal::sign(nanoseconds);
 
     // 4. Let dayLengthNs be 8.64 × 10^13.
     auto day_length_ns = "86400000000000"_sbigint;
@@ -425,7 +419,7 @@ ThrowCompletionOr<NanosecondsToDaysResult> nanoseconds_to_days(GlobalObject& glo
         // a. Return the Record { [[Days]]: the integral part of nanoseconds / dayLengthNs, [[Nanoseconds]]: (abs(nanoseconds) modulo dayLengthNs) × sign, [[DayLength]]: dayLengthNs }.
         return NanosecondsToDaysResult {
             .days = nanoseconds.divided_by(day_length_ns).quotient.to_double(),
-            .nanoseconds = make_handle(js_bigint(vm, Crypto::SignedBigInteger { nanoseconds.unsigned_value() }.divided_by(day_length_ns).remainder.multiplied_by(Crypto::SignedBigInteger { sign }))),
+            .nanoseconds = make_handle(js_bigint(vm, Crypto::SignedBigInteger { nanoseconds.unsigned_value() }.divided_by(day_length_ns).remainder.multiplied_by(Crypto::SignedBigInteger { (i32)sign }))),
             .day_length = day_length_ns.to_double()
         };
     }
@@ -484,7 +478,7 @@ ThrowCompletionOr<NanosecondsToDaysResult> nanoseconds_to_days(GlobalObject& glo
         day_length_ns = one_day_farther_ns.minus(intermediate_ns);
 
         // c. If (nanoseconds − dayLengthNs) × sign ≥ 0, then
-        if (nanoseconds.minus(day_length_ns).multiplied_by(Crypto::SignedBigInteger { sign }) >= "0"_sbigint) {
+        if (nanoseconds.minus(day_length_ns).multiplied_by(Crypto::SignedBigInteger { (i32)sign }) >= "0"_sbigint) {
             // i. Set nanoseconds to nanoseconds − dayLengthNs.
             nanoseconds = nanoseconds.minus(day_length_ns);