LibJS: Remove the InitializeNumberFormat AO

The Initialize* AOs for Intl formatters were removed some time ago, and
the formatter construction steps are now inlined in the constructors
themselves. InitializeNumberFormat was the one remaining initializer we
still had laying around.

Userland/Libraries/LibJS/Runtime/Intl/NumberFormatConstructor.cpp

@@ -48,95 +48,65 @@ ThrowCompletionOr<NonnullGCPtr<Object>> NumberFormatConstructor::construct(Funct
 {
     auto& vm = this->vm();
 
-    auto locales = vm.argument(0);
-    auto options = vm.argument(1);
+    auto locales_value = vm.argument(0);
+    auto options_value = vm.argument(1);
 
-    // 2. Let numberFormat be ? OrdinaryCreateFromConstructor(newTarget, "%Intl.NumberFormat.prototype%", « [[InitializedNumberFormat]], [[Locale]], [[DataLocale]], [[NumberingSystem]], [[Style]], [[Unit]], [[UnitDisplay]], [[Currency]], [[CurrencyDisplay]], [[CurrencySign]], [[MinimumIntegerDigits]], [[MinimumFractionDigits]], [[MaximumFractionDigits]], [[MinimumSignificantDigits]], [[MaximumSignificantDigits]], [[RoundingType]], [[Notation]], [[CompactDisplay]], [[UseGrouping]], [[SignDisplay]], [[RoundingMode]], [[RoundingIncrement]], [[TrailingZeroDisplay]], [[BoundFormat]] »).
+    // 2. Let numberFormat be ? OrdinaryCreateFromConstructor(newTarget, "%Intl.NumberFormat.prototype%", « [[InitializedNumberFormat]], [[Locale]], [[LocaleData]], [[NumberingSystem]], [[Style]], [[Unit]], [[UnitDisplay]], [[Currency]], [[CurrencyDisplay]], [[CurrencySign]], [[MinimumIntegerDigits]], [[MinimumFractionDigits]], [[MaximumFractionDigits]], [[MinimumSignificantDigits]], [[MaximumSignificantDigits]], [[RoundingType]], [[Notation]], [[CompactDisplay]], [[UseGrouping]], [[SignDisplay]], [[RoundingIncrement]], [[RoundingMode]], [[ComputedRoundingPriority]], [[TrailingZeroDisplay]], [[BoundFormat]] »).
     auto number_format = TRY(ordinary_create_from_constructor<NumberFormat>(vm, new_target, &Intrinsics::intl_number_format_prototype));
 
-    // 3. Perform ? InitializeNumberFormat(numberFormat, locales, options).
-    TRY(initialize_number_format(vm, number_format, locales, options));
-
-    // 4. If the implementation supports the normative optional constructor mode of 4.3 Note 1, then
-    //     a. Let this be the this value.
-    //     b. Return ? ChainNumberFormat(numberFormat, NewTarget, this).
-
-    // 5. Return numberFormat.
-    return number_format;
-}
-
-// 15.2.2 Intl.NumberFormat.supportedLocalesOf ( locales [ , options ] ), https://tc39.es/ecma402/#sec-intl.numberformat.supportedlocalesof
-JS_DEFINE_NATIVE_FUNCTION(NumberFormatConstructor::supported_locales_of)
-{
-    auto locales = vm.argument(0);
-    auto options = vm.argument(1);
-
-    // 1. Let availableLocales be %NumberFormat%.[[AvailableLocales]].
-
-    // 2. Let requestedLocales be ? CanonicalizeLocaleList(locales).
-    auto requested_locales = TRY(canonicalize_locale_list(vm, locales));
-
-    // 3. Return ? FilterLocales(availableLocales, requestedLocales, options).
-    return TRY(filter_locales(vm, requested_locales, options));
-}
-
-// 15.1.2 InitializeNumberFormat ( numberFormat, locales, options ), https://tc39.es/ecma402/#sec-initializenumberformat
-ThrowCompletionOr<NonnullGCPtr<NumberFormat>> initialize_number_format(VM& vm, NumberFormat& number_format, Value locales_value, Value options_value)
-{
-    // 1. Let requestedLocales be ? CanonicalizeLocaleList(locales).
+    // 3. Let requestedLocales be ? CanonicalizeLocaleList(locales).
     auto requested_locales = TRY(canonicalize_locale_list(vm, locales_value));
 
-    // 2. Set options to ? CoerceOptionsToObject(options).
+    // 4. Set options to ? CoerceOptionsToObject(options).
     auto* options = TRY(coerce_options_to_object(vm, options_value));
 
-    // 3. Let opt be a new Record.
+    // 5. Let opt be a new Record.
     LocaleOptions opt {};
 
-    // 4. Let matcher be ? GetOption(options, "localeMatcher", string, « "lookup", "best fit" », "best fit").
+    // 6. Let matcher be ? GetOption(options, "localeMatcher", string, « "lookup", "best fit" », "best fit").
     auto matcher = TRY(get_option(vm, *options, vm.names.localeMatcher, OptionType::String, { "lookup"sv, "best fit"sv }, "best fit"sv));
 
-    // 5. Set opt.[[localeMatcher]] to matcher.
+    // 7. Set opt.[[localeMatcher]] to matcher.
     opt.locale_matcher = matcher;
 
-    // 6. Let numberingSystem be ? GetOption(options, "numberingSystem", string, empty, undefined).
+    // 8. Let numberingSystem be ? GetOption(options, "numberingSystem", string, empty, undefined).
     auto numbering_system = TRY(get_option(vm, *options, vm.names.numberingSystem, OptionType::String, {}, Empty {}));
 
-    // 7. If numberingSystem is not undefined, then
+    // 9. If numberingSystem is not undefined, then
     if (!numbering_system.is_undefined()) {
-        // a. If numberingSystem does not match the Unicode Locale Identifier type nonterminal, throw a RangeError exception.
+        // a. If numberingSystem cannot be matched by the type Unicode locale nonterminal, throw a RangeError exception.
         if (!Unicode::is_type_identifier(numbering_system.as_string().utf8_string_view()))
             return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, numbering_system, "numberingSystem"sv);
     }
 
-    // 8. Set opt.[[nu]] to numberingSystem.
+    // 10. Set opt.[[nu]] to numberingSystem.
     opt.nu = locale_key_from_value(numbering_system);
 
-    // 9. Let localeData be %NumberFormat%.[[LocaleData]].
-    // 10. Let r be ResolveLocale(%NumberFormat%.[[AvailableLocales]], requestedLocales, opt, %NumberFormat%.[[RelevantExtensionKeys]], localeData).
+    // 11. Let r be ResolveLocale(%Intl.NumberFormat%.[[AvailableLocales]], requestedLocales, opt, %Intl.NumberFormat%.[[RelevantExtensionKeys]], %Intl.NumberFormat%.[[LocaleData]]).
     auto result = resolve_locale(requested_locales, opt, NumberFormat::relevant_extension_keys());
 
-    // 11. Set numberFormat.[[Locale]] to r.[[locale]].
-    number_format.set_locale(move(result.locale));
+    // 12. Set numberFormat.[[Locale]] to r.[[Locale]].
+    number_format->set_locale(move(result.locale));
 
-    // 12. Set numberFormat.[[LocaleData]] to r.[[LocaleData]].
+    // 13. Set numberFormat.[[LocaleData]] to r.[[LocaleData]].
 
-    // 13. Set numberFormat.[[NumberingSystem]] to r.[[nu]].
+    // 14. Set numberFormat.[[NumberingSystem]] to r.[[nu]].
     if (auto* resolved_numbering_system = result.nu.get_pointer<String>())
-        number_format.set_numbering_system(move(*resolved_numbering_system));
+        number_format->set_numbering_system(move(*resolved_numbering_system));
 
-    // 14. Perform ? SetNumberFormatUnitOptions(numberFormat, options).
+    // 15. Perform ? SetNumberFormatUnitOptions(numberFormat, options).
     TRY(set_number_format_unit_options(vm, number_format, *options));
 
-    // 15. Let style be numberFormat.[[Style]].
-    auto style = number_format.style();
+    // 16. Let style be numberFormat.[[Style]].
+    auto style = number_format->style();
 
     int default_min_fraction_digits = 0;
     int default_max_fraction_digits = 0;
 
-    // 16. If style is "currency", then
+    // 17. If style is "currency", then
     if (style == Unicode::NumberFormatStyle::Currency) {
         // a. Let currency be numberFormat.[[Currency]].
-        auto const& currency = number_format.currency();
+        auto const& currency = number_format->currency();
 
         // b. Let cDigits be CurrencyDigits(currency).
         int digits = currency_digits(currency);
@@ -147,7 +117,7 @@ ThrowCompletionOr<NonnullGCPtr<NumberFormat>> initialize_number_format(VM& vm, N
         // d. Let mxfdDefault be cDigits.
         default_max_fraction_digits = digits;
     }
-    // 17. Else,
+    // 18. Else,
     else {
         // a. Let mnfdDefault be 0.
         default_min_fraction_digits = 0;
@@ -159,68 +129,72 @@ ThrowCompletionOr<NonnullGCPtr<NumberFormat>> initialize_number_format(VM& vm, N
         default_max_fraction_digits = style == Unicode::NumberFormatStyle::Percent ? 0 : 3;
     }
 
-    // 18. Let notation be ? GetOption(options, "notation", string, « "standard", "scientific", "engineering", "compact" », "standard").
+    // 19. Let notation be ? GetOption(options, "notation", string, « "standard", "scientific", "engineering", "compact" », "standard").
     auto notation = TRY(get_option(vm, *options, vm.names.notation, OptionType::String, { "standard"sv, "scientific"sv, "engineering"sv, "compact"sv }, "standard"sv));
 
-    // 19. Set numberFormat.[[Notation]] to notation.
-    number_format.set_notation(notation.as_string().utf8_string_view());
+    // 20. Set numberFormat.[[Notation]] to notation.
+    number_format->set_notation(notation.as_string().utf8_string_view());
 
-    // 20. Perform ? SetNumberFormatDigitOptions(numberFormat, options, mnfdDefault, mxfdDefault, notation).
-    TRY(set_number_format_digit_options(vm, number_format, *options, default_min_fraction_digits, default_max_fraction_digits, number_format.notation()));
+    // 21. Perform ? SetNumberFormatDigitOptions(numberFormat, options, mnfdDefault, mxfdDefault, notation).
+    TRY(set_number_format_digit_options(vm, number_format, *options, default_min_fraction_digits, default_max_fraction_digits, number_format->notation()));
 
-    // 21. Let compactDisplay be ? GetOption(options, "compactDisplay", string, « "short", "long" », "short").
+    // 22. Let compactDisplay be ? GetOption(options, "compactDisplay", string, « "short", "long" », "short").
     auto compact_display = TRY(get_option(vm, *options, vm.names.compactDisplay, OptionType::String, { "short"sv, "long"sv }, "short"sv));
 
-    // 22. Let defaultUseGrouping be "auto".
+    // 23. Let defaultUseGrouping be "auto".
     auto default_use_grouping = "auto"sv;
 
-    // 23. If notation is "compact", then
-    if (number_format.notation() == Unicode::Notation::Compact) {
+    // 24. If notation is "compact", then
+    if (number_format->notation() == Unicode::Notation::Compact) {
         // a. Set numberFormat.[[CompactDisplay]] to compactDisplay.
-        number_format.set_compact_display(compact_display.as_string().utf8_string_view());
+        number_format->set_compact_display(compact_display.as_string().utf8_string_view());
 
         // b. Set defaultUseGrouping to "min2".
         default_use_grouping = "min2"sv;
     }
 
-    // 24. NOTE: For historical reasons, the strings "true" and "false" are accepted and replaced with the default value.
-    // 25. Let useGrouping be ? GetBooleanOrStringNumberFormatOption(options, "useGrouping", « "min2", "auto", "always", "true", "false" », defaultUseGrouping).
+    // 25. NOTE: For historical reasons, the strings "true" and "false" are accepted and replaced with the default value.
+    // 26. Let useGrouping be ? GetBooleanOrStringNumberFormatOption(options, "useGrouping", « "min2", "auto", "always", "true", "false" », defaultUseGrouping).
     auto use_grouping = TRY(get_boolean_or_string_number_format_option(vm, *options, vm.names.useGrouping, { "min2"sv, "auto"sv, "always"sv, "true"sv, "false"sv }, default_use_grouping));
 
-    // 26. If useGrouping is "true" or useGrouping is "false", set useGrouping to defaultUseGrouping.
+    // 27. If useGrouping is "true" or useGrouping is "false", set useGrouping to defaultUseGrouping.
     if (auto const* use_grouping_string = use_grouping.get_pointer<StringView>()) {
         if (use_grouping_string->is_one_of("true"sv, "false"sv))
             use_grouping = default_use_grouping;
     }
 
-    // 27. If useGrouping is true, set useGrouping to "always".
+    // 28. If useGrouping is true, set useGrouping to "always".
     if (auto const* use_grouping_boolean = use_grouping.get_pointer<bool>()) {
         if (*use_grouping_boolean)
             use_grouping = "always"sv;
     }
 
-    // 28. Set numberFormat.[[UseGrouping]] to useGrouping.
-    number_format.set_use_grouping(use_grouping);
+    // 29. Set numberFormat.[[UseGrouping]] to useGrouping.
+    number_format->set_use_grouping(use_grouping);
 
-    // 29. Let signDisplay be ? GetOption(options, "signDisplay", string, « "auto", "never", "always", "exceptZero, "negative" », "auto").
+    // 30. Let signDisplay be ? GetOption(options, "signDisplay", string, « "auto", "never", "always", "exceptZero", "negative" », "auto").
     auto sign_display = TRY(get_option(vm, *options, vm.names.signDisplay, OptionType::String, { "auto"sv, "never"sv, "always"sv, "exceptZero"sv, "negative"sv }, "auto"sv));
 
-    // 30. Set numberFormat.[[SignDisplay]] to signDisplay.
-    number_format.set_sign_display(sign_display.as_string().utf8_string_view());
+    // 31. Set numberFormat.[[SignDisplay]] to signDisplay.
+    number_format->set_sign_display(sign_display.as_string().utf8_string_view());
+
+    // 32. If the implementation supports the normative optional constructor mode of 4.3 Note 1, then
+    //     a. Let this be the this value.
+    //     b. Return ? ChainNumberFormat(numberFormat, NewTarget, this).
 
     // Non-standard, create an ICU number formatter for this Intl object.
     auto formatter = Unicode::NumberFormat::create(
-        number_format.locale(),
-        number_format.numbering_system(),
-        number_format.display_options(),
-        number_format.rounding_options());
-    number_format.set_formatter(move(formatter));
+        number_format->locale(),
+        number_format->numbering_system(),
+        number_format->display_options(),
+        number_format->rounding_options());
+    number_format->set_formatter(move(formatter));
 
-    // 31. Return numberFormat.
+    // 33. Return numberFormat.
     return number_format;
 }
 
-// 15.1.3 SetNumberFormatDigitOptions ( intlObj, options, mnfdDefault, mxfdDefault, notation ), https://tc39.es/ecma402/#sec-setnfdigitoptions
+// 15.1.2 SetNumberFormatDigitOptions ( intlObj, options, mnfdDefault, mxfdDefault, notation ), https://tc39.es/ecma402/#sec-setnfdigitoptions
 ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase& intl_object, Object const& options, int default_min_fraction_digits, int default_max_fraction_digits, Unicode::Notation notation)
 {
     // 1. Let mnid be ? GetNumberOption(options, "minimumIntegerDigits,", 1, 21, 1).
@@ -275,25 +249,19 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
     // 16. Set intlObj.[[TrailingZeroDisplay]] to trailingZeroDisplay.
     intl_object.set_trailing_zero_display(trailing_zero_display.as_string().utf8_string_view());
 
-    // 17. If mnsd is not undefined or mxsd is not undefined, then
-    //     a. Let hasSd be true.
-    // 18. Else,
-    //     a. Let hasSd be false.
+    // 17. If mnsd is undefined and mxsd is undefined, let hasSd be false. Otherwise, let hasSd be true.
     bool has_significant_digits = !min_significant_digits.is_undefined() || !max_significant_digits.is_undefined();
 
-    // 19. If mnfd is not undefined or mxfd is not undefined, then
-    //     a. Let hasFd be true.
-    // 20. Else,
-    //     a. Let hasFd be false.
+    // 18. If mnfd is undefined and mxsd is undefined, let hasFd be false. Otherwise, let hasFd be true.
     bool has_fraction_digits = !min_fraction_digits.is_undefined() || !max_fraction_digits.is_undefined();
 
-    // 21. Let needSd be true.
+    // 19. Let needSd be true.
     bool need_significant_digits = true;
 
-    // 22. Let needFd be true.
+    // 20. Let needFd be true.
     bool need_fraction_digits = true;
 
-    // 23. If roundingPriority is "auto", then
+    // 21. If roundingPriority is "auto", then
     if (rounding_priority == "auto"sv) {
         // a. Set needSd to hasSd.
         need_significant_digits = has_significant_digits;
@@ -305,7 +273,7 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
         }
     }
 
-    // 24. If needSd is true, then
+    // 22. If needSd is true, then
     if (need_significant_digits) {
         // a. If hasSd is true, then
         if (has_significant_digits) {
@@ -327,7 +295,7 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
         }
     }
 
-    // 25. If needFd is true, then
+    // 23. If needFd is true, then
     if (need_fraction_digits) {
         // a. If hasFd is true, then
         if (has_fraction_digits) {
@@ -363,7 +331,7 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
         }
     }
 
-    // 26. If needSd is false and needFd is false, then
+    // 24. If needSd is false and needFd is false, then
     if (!need_significant_digits && !need_fraction_digits) {
         // a. Set intlObj.[[MinimumFractionDigits]] to 0.
         intl_object.set_min_fraction_digits(0);
@@ -377,48 +345,48 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
         // d. Set intlObj.[[MaximumSignificantDigits]] to 2.
         intl_object.set_max_significant_digits(2);
 
-        // e. Set intlObj.[[RoundingType]] to morePrecision.
+        // e. Set intlObj.[[RoundingType]] to MORE-PRECISION.
         intl_object.set_rounding_type(Unicode::RoundingType::MorePrecision);
 
         // f. Set intlObj.[[ComputedRoundingPriority]] to "morePrecision".
         intl_object.set_computed_rounding_priority(NumberFormatBase::ComputedRoundingPriority::MorePrecision);
     }
-    // 27. Else if roundingPriority is "morePrecision", then
+    // 25. Else if roundingPriority is "morePrecision", then
     else if (rounding_priority == "morePrecision"sv) {
-        // a. Set intlObj.[[RoundingType]] to morePrecision.
+        // a. Set intlObj.[[RoundingType]] to MORE-PRECISION.
         intl_object.set_rounding_type(Unicode::RoundingType::MorePrecision);
 
         // b. Set intlObj.[[ComputedRoundingPriority]] to "morePrecision".
         intl_object.set_computed_rounding_priority(NumberFormatBase::ComputedRoundingPriority::MorePrecision);
     }
-    // 28. Else if roundingPriority is "lessPrecision", then
+    // 26. Else if roundingPriority is "lessPrecision", then
     else if (rounding_priority == "lessPrecision"sv) {
-        // a. Set intlObj.[[RoundingType]] to lessPrecision.
+        // a. Set intlObj.[[RoundingType]] to LESS-PRECISION.
         intl_object.set_rounding_type(Unicode::RoundingType::LessPrecision);
 
         // b. Set intlObj.[[ComputedRoundingPriority]] to "lessPrecision".
         intl_object.set_computed_rounding_priority(NumberFormatBase::ComputedRoundingPriority::LessPrecision);
     }
-    // 29. Else if hasSd is true, then
+    // 27. Else if hasSd is true, then
     else if (has_significant_digits) {
-        // a. Set intlObj.[[RoundingType]] to significantDigits.
+        // a. Set intlObj.[[RoundingType]] to SIGNIFICANT-DIGITS.
         intl_object.set_rounding_type(Unicode::RoundingType::SignificantDigits);
 
         // b. Set intlObj.[[ComputedRoundingPriority]] to "auto".
         intl_object.set_computed_rounding_priority(NumberFormatBase::ComputedRoundingPriority::Auto);
     }
-    // 30. Else,
+    // 28. Else,
     else {
-        // a. Set intlObj.[[RoundingType]] to fractionDigits.
+        // a. Set intlObj.[[RoundingType]] to FRACTION-DIGITS.
         intl_object.set_rounding_type(Unicode::RoundingType::FractionDigits);
 
         // b. Set intlObj.[[ComputedRoundingPriority]] to "auto".
         intl_object.set_computed_rounding_priority(NumberFormatBase::ComputedRoundingPriority::Auto);
     }
 
-    // 31. If roundingIncrement is not 1, then
+    // 29. If roundingIncrement is not 1, then
     if (rounding_increment != 1) {
-        // a. If intlObj.[[RoundingType]] is not fractionDigits, throw a TypeError exception.
+        // a. If intlObj.[[RoundingType]] is not FRACTION-DIGITS, throw a TypeError exception.
         if (intl_object.rounding_type() != Unicode::RoundingType::FractionDigits)
             return vm.throw_completion<TypeError>(ErrorType::IntlInvalidRoundingIncrementForRoundingType, *rounding_increment, intl_object.rounding_type_string());
 
@@ -427,59 +395,59 @@ ThrowCompletionOr<void> set_number_format_digit_options(VM& vm, NumberFormatBase
             return vm.throw_completion<RangeError>(ErrorType::IntlInvalidRoundingIncrementForFractionDigits, *rounding_increment);
     }
 
+    // 30. Return UNUSED.
     return {};
 }
 
-// 15.1.4 SetNumberFormatUnitOptions ( intlObj, options ), https://tc39.es/ecma402/#sec-setnumberformatunitoptions
+// 15.1.3 SetNumberFormatUnitOptions ( intlObj, options ), https://tc39.es/ecma402/#sec-setnumberformatunitoptions
 ThrowCompletionOr<void> set_number_format_unit_options(VM& vm, NumberFormat& intl_object, Object const& options)
 {
-    // 1. Assert: Type(intlObj) is Object.
-    // 2. Assert: Type(options) is Object.
-
-    // 3. Let style be ? GetOption(options, "style", string, « "decimal", "percent", "currency", "unit" », "decimal").
+    // 1. Let style be ? GetOption(options, "style", string, « "decimal", "percent", "currency", "unit" », "decimal").
     auto style = TRY(get_option(vm, options, vm.names.style, OptionType::String, { "decimal"sv, "percent"sv, "currency"sv, "unit"sv }, "decimal"sv));
 
-    // 4. Set intlObj.[[Style]] to style.
+    // 2. Set intlObj.[[Style]] to style.
     intl_object.set_style(style.as_string().utf8_string_view());
 
-    // 5. Let currency be ? GetOption(options, "currency", string, empty, undefined).
+    // 3. Let currency be ? GetOption(options, "currency", string, empty, undefined).
     auto currency = TRY(get_option(vm, options, vm.names.currency, OptionType::String, {}, Empty {}));
 
-    // 6. If currency is undefined, then
+    // 4. If currency is undefined, then
     if (currency.is_undefined()) {
         // a. If style is "currency", throw a TypeError exception.
         if (intl_object.style() == Unicode::NumberFormatStyle::Currency)
             return vm.throw_completion<TypeError>(ErrorType::IntlOptionUndefined, "currency"sv, "style"sv, style);
     }
-    // 7. Else,
+    // 5. Else,
     //     a. If IsWellFormedCurrencyCode(currency) is false, throw a RangeError exception.
-    else if (!is_well_formed_currency_code(currency.as_string().utf8_string_view()))
+    else if (!is_well_formed_currency_code(currency.as_string().utf8_string_view())) {
         return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, currency, "currency"sv);
+    }
 
-    // 8. Let currencyDisplay be ? GetOption(options, "currencyDisplay", string, « "code", "symbol", "narrowSymbol", "name" », "symbol").
+    // 6. Let currencyDisplay be ? GetOption(options, "currencyDisplay", string, « "code", "symbol", "narrowSymbol", "name" », "symbol").
     auto currency_display = TRY(get_option(vm, options, vm.names.currencyDisplay, OptionType::String, { "code"sv, "symbol"sv, "narrowSymbol"sv, "name"sv }, "symbol"sv));
 
-    // 9. Let currencySign be ? GetOption(options, "currencySign", string, « "standard", "accounting" », "standard").
+    // 7. Let currencySign be ? GetOption(options, "currencySign", string, « "standard", "accounting" », "standard").
     auto currency_sign = TRY(get_option(vm, options, vm.names.currencySign, OptionType::String, { "standard"sv, "accounting"sv }, "standard"sv));
 
-    // 10. Let unit be ? GetOption(options, "unit", string, empty, undefined).
+    // 8. Let unit be ? GetOption(options, "unit", string, empty, undefined).
     auto unit = TRY(get_option(vm, options, vm.names.unit, OptionType::String, {}, Empty {}));
 
-    // 11. If unit is undefined, then
+    // 9. If unit is undefined, then
     if (unit.is_undefined()) {
         // a. If style is "unit", throw a TypeError exception.
         if (intl_object.style() == Unicode::NumberFormatStyle::Unit)
             return vm.throw_completion<TypeError>(ErrorType::IntlOptionUndefined, "unit"sv, "style"sv, style);
     }
-    // 12. Else,
-    //     a. If ! IsWellFormedUnitIdentifier(unit) is false, throw a RangeError exception.
-    else if (!is_well_formed_unit_identifier(unit.as_string().utf8_string_view()))
+    // 10. Else,
+    //     a. If IsWellFormedUnitIdentifier(unit) is false, throw a RangeError exception.
+    else if (!is_well_formed_unit_identifier(unit.as_string().utf8_string_view())) {
         return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, unit, "unit"sv);
+    }
 
-    // 13. Let unitDisplay be ? GetOption(options, "unitDisplay", string, « "short", "narrow", "long" », "short").
+    // 11. Let unitDisplay be ? GetOption(options, "unitDisplay", string, « "short", "narrow", "long" », "short").
     auto unit_display = TRY(get_option(vm, options, vm.names.unitDisplay, OptionType::String, { "short"sv, "narrow"sv, "long"sv }, "short"sv));
 
-    // 14. If style is "currency", then
+    // 12. If style is "currency", then
     if (intl_object.style() == Unicode::NumberFormatStyle::Currency) {
         // a. Set intlObj.[[Currency]] to the ASCII-uppercase of currency.
         intl_object.set_currency(MUST(currency.as_string().utf8_string().to_uppercase()));
@@ -491,7 +459,7 @@ ThrowCompletionOr<void> set_number_format_unit_options(VM& vm, NumberFormat& int
         intl_object.set_currency_sign(currency_sign.as_string().utf8_string_view());
     }
 
-    // 15. If style is "unit", then
+    // 13. If style is "unit", then
     if (intl_object.style() == Unicode::NumberFormatStyle::Unit) {
         // a. Set intlObj.[[Unit]] to unit.
         intl_object.set_unit(unit.as_string().utf8_string());
@@ -500,7 +468,23 @@ ThrowCompletionOr<void> set_number_format_unit_options(VM& vm, NumberFormat& int
         intl_object.set_unit_display(unit_display.as_string().utf8_string_view());
     }
 
+    // 14. Return UNUSED.
     return {};
 }
 
+// 15.2.2 Intl.NumberFormat.supportedLocalesOf ( locales [ , options ] ), https://tc39.es/ecma402/#sec-intl.numberformat.supportedlocalesof
+JS_DEFINE_NATIVE_FUNCTION(NumberFormatConstructor::supported_locales_of)
+{
+    auto locales = vm.argument(0);
+    auto options = vm.argument(1);
+
+    // 1. Let availableLocales be %NumberFormat%.[[AvailableLocales]].
+
+    // 2. Let requestedLocales be ? CanonicalizeLocaleList(locales).
+    auto requested_locales = TRY(canonicalize_locale_list(vm, locales));
+
+    // 3. Return ? FilterLocales(availableLocales, requestedLocales, options).
+    return TRY(filter_locales(vm, requested_locales, options));
+}
+
 }

Userland/Libraries/LibJS/Runtime/Intl/NumberFormatConstructor.h

@@ -30,7 +30,6 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(supported_locales_of);
 };
 
-ThrowCompletionOr<NonnullGCPtr<NumberFormat>> initialize_number_format(VM&, NumberFormat&, Value locales_value, Value options_value);
 ThrowCompletionOr<void> set_number_format_digit_options(VM&, NumberFormatBase& intl_object, Object const& options, int default_min_fraction_digits, int default_max_fraction_digits, Unicode::Notation notation);
 ThrowCompletionOr<void> set_number_format_unit_options(VM&, NumberFormat& intl_object, Object const& options);