LibJS: Convert Calendar AOs to ThrowCompletionOr

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

@@ -7,6 +7,7 @@
 
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Array.h>
+#include <LibJS/Runtime/Completion.h>
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/Temporal/AbstractOperations.h>
 #include <LibJS/Runtime/Temporal/Calendar.h>
@@ -29,7 +30,7 @@ Calendar::Calendar(String identifier, Object& prototype)
 }
 
 // 12.1.1 CreateTemporalCalendar ( identifier [ , newTarget ] ), https://tc39.es/proposal-temporal/#sec-temporal-createtemporalcalendar
-Calendar* create_temporal_calendar(GlobalObject& global_object, String const& identifier, FunctionObject const* new_target)
+ThrowCompletionOr<Calendar*> create_temporal_calendar(GlobalObject& global_object, String const& identifier, FunctionObject const* new_target)
 {
     // 1. Assert: ! IsBuiltinCalendar(identifier) is true.
     VERIFY(is_builtin_calendar(identifier));
@@ -40,7 +41,7 @@ Calendar* create_temporal_calendar(GlobalObject& global_object, String const& id
 
     // 3. Let object be ? OrdinaryCreateFromConstructor(newTarget, "%Temporal.Calendar.prototype%", « [[InitializedTemporalCalendar]], [[Identifier]] »).
     // 4. Set object.[[Identifier]] to identifier.
-    auto* object = TRY_OR_DISCARD(ordinary_create_from_constructor<Calendar>(global_object, *new_target, &GlobalObject::temporal_calendar_prototype, identifier));
+    auto* object = TRY(ordinary_create_from_constructor<Calendar>(global_object, *new_target, &GlobalObject::temporal_calendar_prototype, identifier));
 
     // 5. Return object.
     return object;
@@ -59,22 +60,20 @@ bool is_builtin_calendar(String const& identifier)
 }
 
 // 12.1.3 GetBuiltinCalendar ( id ), https://tc39.es/proposal-temporal/#sec-temporal-getbuiltincalendar
-Calendar* get_builtin_calendar(GlobalObject& global_object, String const& identifier)
+ThrowCompletionOr<Calendar*> get_builtin_calendar(GlobalObject& global_object, String const& identifier)
 {
     auto& vm = global_object.vm();
 
     // 1. If ! IsBuiltinCalendar(id) is false, throw a RangeError exception.
-    if (!is_builtin_calendar(identifier)) {
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidCalendarIdentifier, identifier);
-        return {};
-    }
+    if (!is_builtin_calendar(identifier))
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidCalendarIdentifier, identifier);
 
     // 2. Return ? Construct(%Temporal.Calendar%, « id »).
     MarkedValueList arguments(vm.heap());
     arguments.append(js_string(vm, identifier));
     auto calendar = vm.construct(*global_object.temporal_calendar_constructor(), *global_object.temporal_calendar_constructor(), move(arguments));
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
     return static_cast<Calendar*>(&calendar.as_object());
 }
 
@@ -82,18 +81,18 @@ Calendar* get_builtin_calendar(GlobalObject& global_object, String const& identi
 Calendar* get_iso8601_calendar(GlobalObject& global_object)
 {
     // 1. Return ! GetBuiltinCalendar("iso8601").
-    return get_builtin_calendar(global_object, "iso8601");
+    return get_builtin_calendar(global_object, "iso8601").release_value();
 }
 
 // 12.1.5 CalendarFields ( calendar, fieldNames ), https://tc39.es/proposal-temporal/#sec-temporal-calendarfields
-Vector<String> calendar_fields(GlobalObject& global_object, Object& calendar, Vector<StringView> const& field_names)
+ThrowCompletionOr<Vector<String>> calendar_fields(GlobalObject& global_object, Object& calendar, Vector<StringView> const& field_names)
 {
     auto& vm = global_object.vm();
 
     // 1. Let fields be ? GetMethod(calendar, "fields").
     auto fields = Value(&calendar).get_method(global_object, vm.names.fields);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 2. Let fieldsArray be ! CreateArrayFromList(fieldNames).
     auto field_names_values = MarkedValueList { vm.heap() };
@@ -105,12 +104,12 @@ Vector<String> calendar_fields(GlobalObject& global_object, Object& calendar, Ve
     if (fields) {
         // a. Set fieldsArray to ? Call(fields, calendar, « fieldsArray »).
         fields_array = vm.call(*fields, &calendar, fields_array);
-        if (vm.exception())
-            return {};
+        if (auto* exception = vm.exception())
+            return throw_completion(exception->value());
     }
 
     // 4. Return ? IterableToListOfType(fieldsArray, « String »).
-    auto list = TRY_OR_DISCARD(iterable_to_list_of_type(global_object, fields_array, { OptionType::String }));
+    auto list = TRY(iterable_to_list_of_type(global_object, fields_array, { OptionType::String }));
 
     Vector<String> result;
     for (auto& value : list)
@@ -119,171 +118,187 @@ Vector<String> calendar_fields(GlobalObject& global_object, Object& calendar, Ve
 }
 
 // 12.1.9 CalendarYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendaryear
-double calendar_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<double> calendar_year(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Let result be ? Invoke(calendar, "year", « dateLike »).
     auto result = Value(&calendar).invoke(global_object, vm.names.year, &date_like);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If result is undefined, throw a RangeError exception.
-    if (result.is_undefined()) {
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.year.as_string(), vm.names.undefined.as_string());
-        return {};
-    }
+    if (result.is_undefined())
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.year.as_string(), vm.names.undefined.as_string());
 
     // 4. Return ? ToIntegerThrowOnInfinity(result).
-    return TRY_OR_DISCARD(to_integer_throw_on_infinity(global_object, result, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.year.as_string(), vm.names.Infinity.as_string()));
+    return TRY(to_integer_throw_on_infinity(global_object, result, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.year.as_string(), vm.names.Infinity.as_string()));
 }
 
 // 12.1.10 CalendarMonth ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarmonth
-double calendar_month(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<double> calendar_month(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Let result be ? Invoke(calendar, "month", « dateLike »).
     auto result = Value(&calendar).invoke(global_object, vm.names.month, &date_like);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If result is undefined, throw a RangeError exception.
-    if (result.is_undefined()) {
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.month.as_string(), vm.names.undefined.as_string());
-        return {};
-    }
+    if (result.is_undefined())
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.month.as_string(), vm.names.undefined.as_string());
 
     // 4. Return ? ToPositiveInteger(result).
-    return TRY_OR_DISCARD(to_positive_integer(global_object, result));
+    return TRY(to_positive_integer(global_object, result));
 }
 
 // 12.1.11 CalendarMonthCode ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarmonthcode
-String calendar_month_code(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<String> calendar_month_code(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Let result be ? Invoke(calendar, "monthCode", « dateLike »).
     auto result = Value(&calendar).invoke(global_object, vm.names.monthCode, &date_like);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If result is undefined, throw a RangeError exception.
-    if (result.is_undefined()) {
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.monthCode.as_string(), vm.names.undefined.as_string());
-        return {};
-    }
+    if (result.is_undefined())
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.monthCode.as_string(), vm.names.undefined.as_string());
 
     // 4. Return ? ToString(result).
     return result.to_string(global_object);
 }
 
 // 12.1.12 CalendarDay ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarday
-double calendar_day(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<double> calendar_day(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Let result be ? Invoke(calendar, "day", « dateLike »).
     auto result = Value(&calendar).invoke(global_object, vm.names.day, &date_like);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If result is undefined, throw a RangeError exception.
-    if (result.is_undefined()) {
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.day.as_string(), vm.names.undefined.as_string());
-        return {};
-    }
+    if (result.is_undefined())
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.day.as_string(), vm.names.undefined.as_string());
 
     // 4. Return ? ToPositiveInteger(result).
-    return TRY_OR_DISCARD(to_positive_integer(global_object, result));
+    return TRY(to_positive_integer(global_object, result));
 }
 
 // 12.1.13 CalendarDayOfWeek ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendardayofweek
-Value calendar_day_of_week(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_day_of_week(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "dayOfWeek", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.dayOfWeek, &date_like);
+    auto day_of_week = Value(&calendar).invoke(global_object, vm.names.dayOfWeek, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return day_of_week;
 }
 
 // 12.1.14 CalendarDayOfYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendardayofyear
-Value calendar_day_of_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_day_of_year(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "dayOfYear", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.dayOfYear, &date_like);
+    auto day_of_year = Value(&calendar).invoke(global_object, vm.names.dayOfYear, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return day_of_year;
 }
 
 // 12.1.15 CalendarWeekOfYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarweekofyear
-Value calendar_week_of_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_week_of_year(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "weekOfYear", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.weekOfYear, &date_like);
+    auto week_of_year = Value(&calendar).invoke(global_object, vm.names.weekOfYear, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return week_of_year;
 }
 
 // 12.1.16 CalendarDaysInWeek ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendardaysinweek
-Value calendar_days_in_week(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_days_in_week(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "daysInWeek", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.daysInWeek, &date_like);
+    auto days_in_week = Value(&calendar).invoke(global_object, vm.names.daysInWeek, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return days_in_week;
 }
 
 // 12.1.17 CalendarDaysInMonth ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendardaysinmonth
-Value calendar_days_in_month(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_days_in_month(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "daysInMonth", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.daysInMonth, &date_like);
+    auto days_in_month = Value(&calendar).invoke(global_object, vm.names.daysInMonth, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return days_in_month;
 }
 
 // 12.1.18 CalendarDaysInYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendardaysinyear
-Value calendar_days_in_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_days_in_year(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "daysInYear", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.daysInYear, &date_like);
+    auto days_in_year = Value(&calendar).invoke(global_object, vm.names.daysInYear, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return days_in_year;
 }
 
 // 12.1.19 CalendarMonthsInYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarmonthsinyear
-Value calendar_months_in_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_months_in_year(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "monthsInYear", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.monthsInYear, &date_like);
+    auto months_in_year = Value(&calendar).invoke(global_object, vm.names.monthsInYear, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return months_in_year;
 }
 
 // 12.1.20 CalendarInLeapYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarinleapyear
-Value calendar_in_leap_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_in_leap_year(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
     // 1. Assert: Type(calendar) is Object.
 
     // 2. Return ? Invoke(calendar, "inLeapYear", « dateLike »).
-    return Value(&calendar).invoke(global_object, vm.names.inLeapYear, &date_like);
+    auto in_leap_year = Value(&calendar).invoke(global_object, vm.names.inLeapYear, &date_like);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return in_leap_year;
 }
 
 // 15.6.1.2 CalendarEra ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarera
-Value calendar_era(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_era(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
 
@@ -291,14 +306,14 @@ Value calendar_era(GlobalObject& global_object, Object& calendar, Object& date_l
 
     // 2. Let result be ? Invoke(calendar, "era", « dateLike »).
     auto result = Value(&calendar).invoke(global_object, vm.names.era, &date_like);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If result is not undefined, set result to ? ToString(result).
     if (!result.is_undefined()) {
         auto result_string = result.to_string(global_object);
-        if (vm.exception())
-            return {};
+        if (auto* exception = vm.exception())
+            return throw_completion(exception->value());
         result = js_string(vm, move(result_string));
     }
 
@@ -307,7 +322,7 @@ Value calendar_era(GlobalObject& global_object, Object& calendar, Object& date_l
 }
 
 // 15.6.1.3 CalendarEraYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarerayear
-Value calendar_era_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+ThrowCompletionOr<Value> calendar_era_year(GlobalObject& global_object, Object& calendar, Object& date_like)
 {
     auto& vm = global_object.vm();
 
@@ -315,19 +330,19 @@ Value calendar_era_year(GlobalObject& global_object, Object& calendar, Object& d
 
     // 2. Let result be ? Invoke(calendar, "eraYear", « dateLike »).
     auto result = Value(&calendar).invoke(global_object, vm.names.eraYear, &date_like);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If result is not undefined, set result to ? ToIntegerThrowOnInfinity(result).
     if (!result.is_undefined())
-        result = Value(TRY_OR_DISCARD(to_integer_throw_on_infinity(global_object, result, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.eraYear.as_string(), "Infinity"sv)));
+        result = Value(TRY(to_integer_throw_on_infinity(global_object, result, ErrorType::TemporalInvalidCalendarFunctionResult, vm.names.eraYear.as_string(), "Infinity"sv)));
 
     // 4. Return result.
     return result;
 }
 
 // 12.1.21 ToTemporalCalendar ( temporalCalendarLike ), https://tc39.es/proposal-temporal/#sec-temporal-totemporalcalendar
-Object* to_temporal_calendar(GlobalObject& global_object, Value temporal_calendar_like)
+ThrowCompletionOr<Object*> to_temporal_calendar(GlobalObject& global_object, Value temporal_calendar_like)
 {
     auto& vm = global_object.vm();
 
@@ -351,20 +366,21 @@ Object* to_temporal_calendar(GlobalObject& global_object, Value temporal_calenda
 
         // b. If ? HasProperty(temporalCalendarLike, "calendar") is false, return temporalCalendarLike.
         auto has_property = temporal_calendar_like_object.has_property(vm.names.calendar);
-        if (vm.exception())
-            return {};
+        if (auto* exception = vm.exception())
+            return throw_completion(exception->value());
         if (!has_property)
             return &temporal_calendar_like_object;
 
         // c. Set temporalCalendarLike to ? Get(temporalCalendarLike, "calendar").
         temporal_calendar_like = temporal_calendar_like_object.get(vm.names.calendar);
-        if (vm.exception())
-            return {};
+        if (auto* exception = vm.exception())
+            return throw_completion(exception->value());
+
         // d. If Type(temporalCalendarLike) is Object and ? HasProperty(temporalCalendarLike, "calendar") is false, return temporalCalendarLike.
         if (temporal_calendar_like.is_object()) {
             has_property = temporal_calendar_like.as_object().has_property(vm.names.calendar);
-            if (vm.exception())
-                return {};
+            if (auto* exception = vm.exception())
+                return throw_completion(exception->value());
             if (!has_property)
                 return &temporal_calendar_like.as_object();
         }
@@ -372,21 +388,21 @@ Object* to_temporal_calendar(GlobalObject& global_object, Value temporal_calenda
 
     // 2. Let identifier be ? ToString(temporalCalendarLike).
     auto identifier = temporal_calendar_like.to_string(global_object);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If ! IsBuiltinCalendar(identifier) is false, then
     if (!is_builtin_calendar(identifier)) {
         // a. Let identifier be ? ParseTemporalCalendarString(identifier).
-        identifier = TRY_OR_DISCARD(parse_temporal_calendar_string(global_object, identifier));
+        identifier = TRY(parse_temporal_calendar_string(global_object, identifier));
     }
 
     // 4. Return ! CreateTemporalCalendar(identifier).
-    return create_temporal_calendar(global_object, identifier);
+    return create_temporal_calendar(global_object, identifier).release_value();
 }
 
 // 12.1.22 ToTemporalCalendarWithISODefault ( temporalCalendarLike ), https://tc39.es/proposal-temporal/#sec-temporal-totemporalcalendarwithisodefault
-Object* to_temporal_calendar_with_iso_default(GlobalObject& global_object, Value temporal_calendar_like)
+ThrowCompletionOr<Object*> to_temporal_calendar_with_iso_default(GlobalObject& global_object, Value temporal_calendar_like)
 {
     // 1. If temporalCalendarLike is undefined, then
     if (temporal_calendar_like.is_undefined()) {
@@ -398,7 +414,7 @@ Object* to_temporal_calendar_with_iso_default(GlobalObject& global_object, Value
 }
 
 // 12.1.23 GetTemporalCalendarWithISODefault ( item ), https://tc39.es/proposal-temporal/#sec-temporal-gettemporalcalendarwithisodefault
-Object* get_temporal_calendar_with_iso_default(GlobalObject& global_object, Object& item)
+ThrowCompletionOr<Object*> get_temporal_calendar_with_iso_default(GlobalObject& global_object, Object& item)
 {
     auto& vm = global_object.vm();
 
@@ -419,15 +435,15 @@ Object* get_temporal_calendar_with_iso_default(GlobalObject& global_object, Obje
 
     // 2. Let calendar be ? Get(item, "calendar").
     auto calendar = item.get(vm.names.calendar);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. Return ? ToTemporalCalendarWithISODefault(calendar).
     return to_temporal_calendar_with_iso_default(global_object, calendar);
 }
 
 // 12.1.24 DateFromFields ( calendar, fields, options ), https://tc39.es/proposal-temporal/#sec-temporal-datefromfields
-PlainDate* date_from_fields(GlobalObject& global_object, Object& calendar, Object const& fields, Object const& options)
+ThrowCompletionOr<PlainDate*> date_from_fields(GlobalObject& global_object, Object& calendar, Object const& fields, Object const& options)
 {
     auto& vm = global_object.vm();
 
@@ -436,24 +452,22 @@ PlainDate* date_from_fields(GlobalObject& global_object, Object& calendar, Objec
 
     // 3. Let date be ? Invoke(calendar, "dateFromFields", « fields, options »).
     auto date = Value(&calendar).invoke(global_object, vm.names.dateFromFields, &fields, &options);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 4. Perform ? RequireInternalSlot(date, [[InitializedTemporalDate]]).
     auto* date_object = date.to_object(global_object);
-    if (!date_object)
-        return {};
-    if (!is<PlainDate>(date_object)) {
-        vm.throw_exception<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Temporal.PlainDate");
-        return {};
-    }
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    if (!is<PlainDate>(date_object))
+        return vm.throw_completion<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Temporal.PlainDate");
 
     // 5. Return date.
     return static_cast<PlainDate*>(date_object);
 }
 
 // 12.1.25 YearMonthFromFields ( calendar, fields [ , options ] ), https://tc39.es/proposal-temporal/#sec-temporal-yearmonthfromfields
-PlainYearMonth* year_month_from_fields(GlobalObject& global_object, Object& calendar, Object const& fields, Object const* options)
+ThrowCompletionOr<PlainYearMonth*> year_month_from_fields(GlobalObject& global_object, Object& calendar, Object const& fields, Object const* options)
 {
     auto& vm = global_object.vm();
 
@@ -466,24 +480,22 @@ PlainYearMonth* year_month_from_fields(GlobalObject& global_object, Object& cale
 
     // 5. Let yearMonth be ? Invoke(calendar, "yearMonthFromFields", « fields, options »).
     auto year_month = Value(&calendar).invoke(global_object, vm.names.yearMonthFromFields, &fields, options ?: js_undefined());
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 6. Perform ? RequireInternalSlot(yearMonth, [[InitializedTemporalYearMonth]]).
     auto* year_month_object = year_month.to_object(global_object);
-    if (!year_month_object)
-        return {};
-    if (!is<PlainYearMonth>(year_month_object)) {
-        vm.throw_exception<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Temporal.PlainYearMonth");
-        return {};
-    }
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    if (!is<PlainYearMonth>(year_month_object))
+        return vm.throw_completion<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Temporal.PlainYearMonth");
 
     // 7. Return yearMonth.
     return static_cast<PlainYearMonth*>(year_month_object);
 }
 
 // 12.1.26 MonthDayFromFields ( calendar, fields [ , options ] ), https://tc39.es/proposal-temporal/#sec-temporal-monthdayfromfields
-PlainMonthDay* month_day_from_fields(GlobalObject& global_object, Object& calendar, Object const& fields, Object const* options)
+ThrowCompletionOr<PlainMonthDay*> month_day_from_fields(GlobalObject& global_object, Object& calendar, Object const& fields, Object const* options)
 {
     auto& vm = global_object.vm();
 
@@ -496,17 +508,15 @@ PlainMonthDay* month_day_from_fields(GlobalObject& global_object, Object& calend
 
     // 5. Let monthDay be ? Invoke(calendar, "monthDayFromFields", « fields, options »).
     auto month_day = Value(&calendar).invoke(global_object, vm.names.monthDayFromFields, &fields, options ?: js_undefined());
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 6. Perform ? RequireInternalSlot(monthDay, [[InitializedTemporalMonthDay]]).
     auto* month_day_object = month_day.to_object(global_object);
-    if (!month_day_object)
-        return {};
-    if (!is<PlainMonthDay>(month_day_object)) {
-        vm.throw_exception<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Temporal.PlainMonthDay");
-        return {};
-    }
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    if (!is<PlainMonthDay>(month_day_object))
+        return vm.throw_completion<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Temporal.PlainMonthDay");
 
     // 7. Return monthDay.
     return static_cast<PlainMonthDay*>(month_day_object);
@@ -531,7 +541,7 @@ String format_calendar_annotation(StringView id, StringView show_calendar)
 }
 
 // 12.1.28 CalendarEquals ( one, two ), https://tc39.es/proposal-temporal/#sec-temporal-calendarequals
-bool calendar_equals(GlobalObject& global_object, Object& one, Object& two)
+ThrowCompletionOr<bool> calendar_equals(GlobalObject& global_object, Object& one, Object& two)
 {
     auto& vm = global_object.vm();
 
@@ -541,22 +551,24 @@ bool calendar_equals(GlobalObject& global_object, Object& one, Object& two)
 
     // 2. Let calendarOne be ? ToString(one).
     auto calendar_one = Value(&one).to_string(global_object);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+
     // 3. Let calendarTwo be ? ToString(two).
     auto calendar_two = Value(&two).to_string(global_object);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 4. If calendarOne is calendarTwo, return true.
     if (calendar_one == calendar_two)
         return true;
+
     // 5. Return false.
     return false;
 }
 
 // 12.1.29 ConsolidateCalendars ( one, two ), https://tc39.es/proposal-temporal/#sec-temporal-consolidatecalendars
-Object* consolidate_calendars(GlobalObject& global_object, Object& one, Object& two)
+ThrowCompletionOr<Object*> consolidate_calendars(GlobalObject& global_object, Object& one, Object& two)
 {
     auto& vm = global_object.vm();
     // 1. If one and two are the same Object value, return two.
@@ -565,13 +577,13 @@ Object* consolidate_calendars(GlobalObject& global_object, Object& one, Object&
 
     // 2. Let calendarOne be ? ToString(one).
     auto calendar_one = Value(&one).to_string(global_object);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. Let calendarTwo be ? ToString(two).
     auto calendar_two = Value(&two).to_string(global_object);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 4. If calendarOne is calendarTwo, return two.
     if (calendar_one == calendar_two)
@@ -586,8 +598,7 @@ Object* consolidate_calendars(GlobalObject& global_object, Object& one, Object&
         return &one;
 
     // 7. Throw a RangeError exception.
-    vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidCalendar);
-    return {};
+    return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidCalendar);
 }
 
 // 12.1.30 IsISOLeapYear ( year ), https://tc39.es/proposal-temporal/#sec-temporal-isisoleapyear
@@ -720,27 +731,26 @@ String build_iso_month_code(u8 month)
 }
 
 // 12.1.37 ResolveISOMonth ( fields ), https://tc39.es/proposal-temporal/#sec-temporal-resolveisomonth
-double resolve_iso_month(GlobalObject& global_object, Object const& fields)
+ThrowCompletionOr<double> resolve_iso_month(GlobalObject& global_object, Object const& fields)
 {
     auto& vm = global_object.vm();
 
     // 1. Let month be ? Get(fields, "month").
     auto month = fields.get(vm.names.month);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 2. Let monthCode be ? Get(fields, "monthCode").
     auto month_code = fields.get(vm.names.monthCode);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. If monthCode is undefined, then
     if (month_code.is_undefined()) {
         // a. If month is undefined, throw a TypeError exception.
-        if (month.is_undefined()) {
-            vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.month.as_string());
-            return {};
-        }
+        if (month.is_undefined())
+            return vm.throw_completion<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.month.as_string());
+
         // b. Return month.
         return month.as_double();
     }
@@ -748,168 +758,158 @@ double resolve_iso_month(GlobalObject& global_object, Object const& fields)
     // 4. Assert: Type(monthCode) is String.
     VERIFY(month_code.is_string());
     auto& month_code_string = month_code.as_string().string();
+
     // 5. Let monthLength be the length of monthCode.
     auto month_length = month_code_string.length();
+
     // 6. If monthLength is not 3, throw a RangeError exception.
-    if (month_length != 3) {
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
-        return {};
-    }
+    if (month_length != 3)
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
+
     // 7. Let numberPart be the substring of monthCode from 1.
     auto number_part = month_code_string.substring(1);
+
     // 8. Set numberPart to ! ToIntegerOrInfinity(numberPart).
     auto number_part_integer = Value(js_string(vm, move(number_part))).to_integer_or_infinity(global_object);
+
     // 9. If numberPart < 1 or numberPart > 12, throw a RangeError exception.
-    if (number_part_integer < 1 || number_part_integer > 12) {
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
-        return {};
-    }
+    if (number_part_integer < 1 || number_part_integer > 12)
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
+
     // 10. If month is not undefined, and month ≠ numberPart, then
     if (!month.is_undefined() && month.as_double() != number_part_integer) {
         // a. Throw a RangeError exception.
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
-        return {};
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
     }
+
     // 11. If ! SameValueNonNumeric(monthCode, ! BuildISOMonthCode(numberPart)) is false, then
     if (month_code_string != build_iso_month_code(number_part_integer)) {
         // a. Throw a RangeError exception.
-        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
-        return {};
+        return vm.throw_completion<RangeError>(global_object, ErrorType::TemporalInvalidMonthCode);
     }
+
     // 12. Return numberPart.
     return number_part_integer;
 }
 
 // 12.1.38 ISODateFromFields ( fields, options ), https://tc39.es/proposal-temporal/#sec-temporal-isodatefromfields
-Optional<ISODate> iso_date_from_fields(GlobalObject& global_object, Object const& fields, Object const& options)
+ThrowCompletionOr<ISODate> iso_date_from_fields(GlobalObject& global_object, Object const& fields, Object const& options)
 {
     auto& vm = global_object.vm();
 
     // 1. Assert: Type(fields) is Object.
 
     // 2. Let overflow be ? ToTemporalOverflow(options).
-    auto overflow = TRY_OR_DISCARD(to_temporal_overflow(global_object, options));
+    auto overflow = TRY(to_temporal_overflow(global_object, options));
 
     // 3. Set fields to ? PrepareTemporalFields(fields, « "day", "month", "monthCode", "year" », «»).
-    auto* prepared_fields = TRY_OR_DISCARD(prepare_temporal_fields(global_object, fields, { "day", "month", "monthCode", "year" }, {}));
+    auto* prepared_fields = TRY(prepare_temporal_fields(global_object, fields, { "day", "month", "monthCode", "year" }, {}));
 
     // 4. Let year be ? Get(fields, "year").
     auto year = prepared_fields->get(vm.names.year);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 5. If year is undefined, throw a TypeError exception.
-    if (year.is_undefined()) {
-        vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.year.as_string());
-        return {};
-    }
+    if (year.is_undefined())
+        return vm.throw_completion<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.year.as_string());
 
     // 6. Let month be ? ResolveISOMonth(fields).
-    auto month = resolve_iso_month(global_object, *prepared_fields);
-    if (vm.exception())
-        return {};
+    auto month = TRY(resolve_iso_month(global_object, *prepared_fields));
 
     // 7. Let day be ? Get(fields, "day").
     auto day = prepared_fields->get(vm.names.day);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 8. If day is undefined, throw a TypeError exception.
-    if (day.is_undefined()) {
-        vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.day.as_string());
-        return {};
-    }
+    if (day.is_undefined())
+        return vm.throw_completion<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.day.as_string());
 
     // 9. Return ? RegulateISODate(year, month, day, overflow).
-    return regulate_iso_date(global_object, year.as_double(), month, day.as_double(), overflow);
+    auto iso_date = regulate_iso_date(global_object, year.as_double(), month, day.as_double(), overflow);
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    return *iso_date;
 }
 
 // 12.1.39 ISOYearMonthFromFields ( fields, options ), https://tc39.es/proposal-temporal/#sec-temporal-isoyearmonthfromfields
-Optional<ISOYearMonth> iso_year_month_from_fields(GlobalObject& global_object, Object const& fields, Object const& options)
+ThrowCompletionOr<ISOYearMonth> iso_year_month_from_fields(GlobalObject& global_object, Object const& fields, Object const& options)
 {
     auto& vm = global_object.vm();
 
     // 1. Assert: Type(fields) is Object.
 
     // 2. Let overflow be ? ToTemporalOverflow(options).
-    auto overflow = TRY_OR_DISCARD(to_temporal_overflow(global_object, options));
+    auto overflow = TRY(to_temporal_overflow(global_object, options));
 
     // 3. Set fields to ? PrepareTemporalFields(fields, « "month", "monthCode", "year" », «»).
-    auto* prepared_fields = TRY_OR_DISCARD(prepare_temporal_fields(global_object, fields, { "month"sv, "monthCode"sv, "year"sv }, {}));
+    auto* prepared_fields = TRY(prepare_temporal_fields(global_object, fields, { "month"sv, "monthCode"sv, "year"sv }, {}));
 
     // 4. Let year be ? Get(fields, "year").
     auto year = prepared_fields->get(vm.names.year);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 5. If year is undefined, throw a TypeError exception.
-    if (year.is_undefined()) {
-        vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.year.as_string());
-        return {};
-    }
+    if (year.is_undefined())
+        return vm.throw_completion<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.year.as_string());
 
     // 6. Let month be ? ResolveISOMonth(fields).
-    auto month = resolve_iso_month(global_object, *prepared_fields);
-    if (vm.exception())
-        return {};
+    auto month = TRY(resolve_iso_month(global_object, *prepared_fields));
 
     // 7. Let result be ? RegulateISOYearMonth(year, month, overflow).
-    auto result = TRY_OR_DISCARD(regulate_iso_year_month(global_object, year.as_double(), month, overflow));
+    auto result = TRY(regulate_iso_year_month(global_object, year.as_double(), month, overflow));
 
     // 8. Return the Record { [[Year]]: result.[[Year]], [[Month]]: result.[[Month]], [[ReferenceISODay]]: 1 }.
     return ISOYearMonth { .year = result.year, .month = result.month, .reference_iso_day = 1 };
 }
 
 // 12.1.40 ISOMonthDayFromFields ( fields, options ), https://tc39.es/proposal-temporal/#sec-temporal-isomonthdayfromfields
-Optional<ISOMonthDay> iso_month_day_from_fields(GlobalObject& global_object, Object const& fields, Object const& options)
+ThrowCompletionOr<ISOMonthDay> iso_month_day_from_fields(GlobalObject& global_object, Object const& fields, Object const& options)
 {
     auto& vm = global_object.vm();
 
     // 1. Assert: Type(fields) is Object.
 
     // 2. Let overflow be ? ToTemporalOverflow(options).
-    auto overflow = TRY_OR_DISCARD(to_temporal_overflow(global_object, options));
+    auto overflow = TRY(to_temporal_overflow(global_object, options));
 
     // 3. Set fields to ? PrepareTemporalFields(fields, « "day", "month", "monthCode", "year" », «»).
-    auto* prepared_fields = TRY_OR_DISCARD(prepare_temporal_fields(global_object, fields, { "day"sv, "month"sv, "monthCode"sv, "year"sv }, {}));
+    auto* prepared_fields = TRY(prepare_temporal_fields(global_object, fields, { "day"sv, "month"sv, "monthCode"sv, "year"sv }, {}));
 
     // 4. Let month be ? Get(fields, "month").
     auto month_value = prepared_fields->get(vm.names.month);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 5. Let monthCode be ? Get(fields, "monthCode").
     auto month_code = prepared_fields->get(vm.names.monthCode);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 6. Let year be ? Get(fields, "year").
     auto year = prepared_fields->get(vm.names.year);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 7. If month is not undefined, and monthCode and year are both undefined, then
     if (!month_value.is_undefined() && month_code.is_undefined() && year.is_undefined()) {
         // a. Throw a TypeError exception.
-        vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, "monthCode or year");
-        return {};
+        return vm.throw_completion<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, "monthCode or year");
     }
 
     // 8. Set month to ? ResolveISOMonth(fields).
-    auto month = resolve_iso_month(global_object, *prepared_fields);
-    if (vm.exception())
-        return {};
+    auto month = TRY(resolve_iso_month(global_object, *prepared_fields));
 
     // 9. Let day be ? Get(fields, "day").
     auto day = prepared_fields->get(vm.names.day);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 10. If day is undefined, throw a TypeError exception.
-    if (day.is_undefined()) {
-        vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.day.as_string());
-        return {};
-    }
+    if (day.is_undefined())
+        return vm.throw_completion<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.day.as_string());
 
     // 11. Let referenceISOYear be 1972 (the first leap year after the Unix epoch).
     i32 reference_iso_year = 1972;
@@ -926,8 +926,8 @@ Optional<ISOMonthDay> iso_month_day_from_fields(GlobalObject& global_object, Obj
         // a. Let result be ? RegulateISODate(referenceISOYear, month, day, overflow).
         result = regulate_iso_date(global_object, reference_iso_year, month, day.as_double(), overflow);
     }
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 14. Return the Record { [[Month]]: result.[[Month]], [[Day]]: result.[[Day]], [[ReferenceISOYear]]: referenceISOYear }.
     return ISOMonthDay { .month = result->month, .day = result->day, .reference_iso_year = reference_iso_year };
@@ -1006,7 +1006,7 @@ u8 iso_day(Object& temporal_object)
 }
 
 // 12.1.45 DefaultMergeFields ( fields, additionalFields ), https://tc39.es/proposal-temporal/#sec-temporal-defaultmergefields
-Object* default_merge_fields(GlobalObject& global_object, Object const& fields, Object const& additional_fields)
+ThrowCompletionOr<Object*> default_merge_fields(GlobalObject& global_object, Object const& fields, Object const& additional_fields)
 {
     auto& vm = global_object.vm();
 
@@ -1015,8 +1015,8 @@ Object* default_merge_fields(GlobalObject& global_object, Object const& fields,
 
     // 2. Let originalKeys be ? EnumerableOwnPropertyNames(fields, key).
     auto original_keys = fields.enumerable_own_property_names(Object::PropertyKind::Key);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // 3. For each element nextKey of originalKeys, do
     for (auto& next_key : original_keys) {
@@ -1026,8 +1026,8 @@ Object* default_merge_fields(GlobalObject& global_object, Object const& fields,
 
             // i. Let propValue be ? Get(fields, nextKey).
             auto prop_value = fields.get(property_name);
-            if (vm.exception())
-                return {};
+            if (auto* exception = vm.exception())
+                return throw_completion(exception->value());
 
             // ii. If propValue is not undefined, then
             if (!prop_value.is_undefined()) {
@@ -1039,8 +1039,8 @@ Object* default_merge_fields(GlobalObject& global_object, Object const& fields,
 
     // 4. Let newKeys be ? EnumerableOwnPropertyNames(additionalFields, key).
     auto new_keys = additional_fields.enumerable_own_property_names(Object::PropertyKind::Key);
-    if (vm.exception())
-        return {};
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
 
     // IMPLEMENTATION DEFINED: This is an optimization, so we don't have to iterate new_keys three times (worst case), but only once.
     bool new_keys_contains_month_or_month_code_property = false;
@@ -1051,8 +1051,8 @@ Object* default_merge_fields(GlobalObject& global_object, Object const& fields,
 
         // a. Let propValue be ? Get(additionalFields, nextKey).
         auto prop_value = additional_fields.get(property_name);
-        if (vm.exception())
-            return {};
+        if (auto* exception = vm.exception())
+            return throw_completion(exception->value());
 
         // b. If propValue is not undefined, then
         if (!prop_value.is_undefined()) {
@@ -1068,8 +1068,8 @@ Object* default_merge_fields(GlobalObject& global_object, Object const& fields,
     if (!new_keys_contains_month_or_month_code_property) {
         // a. Let month be ? Get(fields, "month").
         auto month = fields.get(vm.names.month);
-        if (vm.exception())
-            return {};
+        if (auto* exception = vm.exception())
+            return throw_completion(exception->value());
 
         // b. If month is not undefined, then
         if (!month.is_undefined()) {
@@ -1079,8 +1079,8 @@ Object* default_merge_fields(GlobalObject& global_object, Object const& fields,
 
         // c. Let monthCode be ? Get(fields, "monthCode").
         auto month_code = fields.get(vm.names.monthCode);
-        if (vm.exception())
-            return {};
+        if (auto* exception = vm.exception())
+            return throw_completion(exception->value());
 
         // d. If monthCode is not undefined, then
         if (!month_code.is_undefined()) {