From d9e044ff0dd86faea3423ebed1eae770959b1559 Mon Sep 17 00:00:00 2001
From: jihndai <73680880+jihndai@users.noreply.github.com>
Date: Sat, 26 Mar 2022 17:08:01 -0400
Subject: [PATCH 1/4] update display names types

---
 src/lib/es2020.intl.d.ts | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/src/lib/es2020.intl.d.ts b/src/lib/es2020.intl.d.ts
index c7d4d725368ea..9a548e9ec4fd7 100644
--- a/src/lib/es2020.intl.d.ts
+++ b/src/lib/es2020.intl.d.ts
@@ -63,7 +63,7 @@ declare namespace Intl {
      *
      * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#locales_argument).
      */
-    type LocalesArgument = UnicodeBCP47LocaleIdentifier | UnicodeBCP47LocaleIdentifier[] | Locale | Locale[] | undefined;
+    type LocalesArgument = UnicodeBCP47LocaleIdentifier | Locale | (UnicodeBCP47LocaleIdentifier | Locale)[] | undefined;
 
     /**
      * An object with some or all of properties of `options` parameter
@@ -295,30 +295,32 @@ declare namespace Intl {
         | "code"
         | "none";
 
-    type ResolvedDisplayNamesType =
+    type DisplayNamesType =
         | "language"
         | "region"
         | "script"
+        | "calendar"
+        | "dateTimeField"
         | "currency";
 
-    type DisplayNamesType =
-        | ResolvedDisplayNamesType
-        | "calendar"
-        | "datetimeField";
+    type DisplayNamesLanguageDisplay =
+        | "dialect"
+        | "standard";
 
     interface DisplayNamesOptions {
-        localeMatcher: RelativeTimeFormatLocaleMatcher;
-        style: RelativeTimeFormatStyle;
+        localeMatcher?: RelativeTimeFormatLocaleMatcher;
+        style?: RelativeTimeFormatStyle;
         type: DisplayNamesType;
-        languageDisplay: "dialect" | "standard";
-        fallback: DisplayNamesFallback;
+        languageDisplay?: DisplayNamesLanguageDisplay;
+        fallback?: DisplayNamesFallback;
     }
 
     interface ResolvedDisplayNamesOptions {
         locale: UnicodeBCP47LocaleIdentifier;
         style: RelativeTimeFormatStyle;
-        type: ResolvedDisplayNamesType;
+        type: DisplayNamesType;
         fallback: DisplayNamesFallback;
+        languageDisplay?: DisplayNamesLanguageDisplay;
     }
 
     interface DisplayNames {
@@ -365,7 +367,7 @@ declare namespace Intl {
          *
          * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DisplayNames/DisplayNames).
          */
-        new(locales?: BCP47LanguageTag | BCP47LanguageTag[], options?: Partial<DisplayNamesOptions>): DisplayNames;
+        new(locales: LocalesArgument, options: DisplayNamesOptions): DisplayNames;
 
         /**
          * Returns an array containing those of the provided locales that are supported in display names without having to fall back to the runtime's default locale.
@@ -380,7 +382,7 @@ declare namespace Intl {
          *
          * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DisplayNames/supportedLocalesOf).
          */
-        supportedLocalesOf(locales: BCP47LanguageTag | BCP47LanguageTag[], options?: {localeMatcher: RelativeTimeFormatLocaleMatcher}): BCP47LanguageTag[];
+        supportedLocalesOf(locales?: LocalesArgument, options?: { localeMatcher?: RelativeTimeFormatLocaleMatcher }): BCP47LanguageTag[];
     };
 
 }

From 4b31db617945cba9d5f2152afd3a6aeab3ba8c39 Mon Sep 17 00:00:00 2001
From: jihndai <73680880+jihndai@users.noreply.github.com>
Date: Sat, 26 Mar 2022 17:19:11 -0400
Subject: [PATCH 2/4] update baselines

---
 tests/baselines/reference/es2020IntlAPIs.types | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tests/baselines/reference/es2020IntlAPIs.types b/tests/baselines/reference/es2020IntlAPIs.types
index fa7ab907a19fc..8cc08f6d8df19 100644
--- a/tests/baselines/reference/es2020IntlAPIs.types
+++ b/tests/baselines/reference/es2020IntlAPIs.types
@@ -128,9 +128,9 @@ console.log(rtf2.format(2, 'day'));
 const regionNamesInEnglish = new Intl.DisplayNames(['en'], { type: 'region' });
 >regionNamesInEnglish : Intl.DisplayNames
 >new Intl.DisplayNames(['en'], { type: 'region' }) : Intl.DisplayNames
->Intl.DisplayNames : { new (locales?: string | string[], options?: Partial<Intl.DisplayNamesOptions>): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
 >Intl : typeof Intl
->DisplayNames : { new (locales?: string | string[], options?: Partial<Intl.DisplayNamesOptions>): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
 >['en'] : string[]
 >'en' : "en"
 >{ type: 'region' } : { type: "region"; }
@@ -140,9 +140,9 @@ const regionNamesInEnglish = new Intl.DisplayNames(['en'], { type: 'region' });
 const regionNamesInTraditionalChinese = new Intl.DisplayNames(['zh-Hant'], { type: 'region' });
 >regionNamesInTraditionalChinese : Intl.DisplayNames
 >new Intl.DisplayNames(['zh-Hant'], { type: 'region' }) : Intl.DisplayNames
->Intl.DisplayNames : { new (locales?: string | string[], options?: Partial<Intl.DisplayNamesOptions>): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
 >Intl : typeof Intl
->DisplayNames : { new (locales?: string | string[], options?: Partial<Intl.DisplayNamesOptions>): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
 >['zh-Hant'] : string[]
 >'zh-Hant' : "zh-Hant"
 >{ type: 'region' } : { type: "region"; }
@@ -197,11 +197,11 @@ console.log(Intl.DisplayNames.supportedLocalesOf(locales1, options1).join(', '))
 >Intl.DisplayNames.supportedLocalesOf(locales1, options1).join(', ') : string
 >Intl.DisplayNames.supportedLocalesOf(locales1, options1).join : (separator?: string) => string
 >Intl.DisplayNames.supportedLocalesOf(locales1, options1) : string[]
->Intl.DisplayNames.supportedLocalesOf : (locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
->Intl.DisplayNames : { new (locales?: string | string[], options?: Partial<Intl.DisplayNamesOptions>): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl.DisplayNames.supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
 >Intl : typeof Intl
->DisplayNames : { new (locales?: string | string[], options?: Partial<Intl.DisplayNamesOptions>): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
->supportedLocalesOf : (locales: string | string[], options?: { localeMatcher: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
 >locales1 : string[]
 >options1 : { readonly localeMatcher: "lookup"; }
 >join : (separator?: string) => string

From 7e3bf00d6e0b16c3b615bacb0408ad2ce619d28e Mon Sep 17 00:00:00 2001
From: jihndai <73680880+jihndai@users.noreply.github.com>
Date: Sat, 26 Mar 2022 17:21:28 -0400
Subject: [PATCH 3/4] add tests and baselines

---
 .../reference/es2020IntlAPIs.errors.txt       | 29 +++++-
 tests/baselines/reference/es2020IntlAPIs.js   | 21 ++++-
 .../reference/es2020IntlAPIs.symbols          | 67 ++++++++++++++
 .../baselines/reference/es2020IntlAPIs.types  | 90 +++++++++++++++++++
 .../conformance/es2020/es2020IntlAPIs.ts      | 12 ++-
 5 files changed, 215 insertions(+), 4 deletions(-)

diff --git a/tests/baselines/reference/es2020IntlAPIs.errors.txt b/tests/baselines/reference/es2020IntlAPIs.errors.txt
index 0c74f13974c62..4508afc98aaf4 100644
--- a/tests/baselines/reference/es2020IntlAPIs.errors.txt
+++ b/tests/baselines/reference/es2020IntlAPIs.errors.txt
@@ -1,7 +1,11 @@
 tests/cases/conformance/es2020/es2020IntlAPIs.ts(45,1): error TS2554: Expected 1-2 arguments, but got 0.
+tests/cases/conformance/es2020/es2020IntlAPIs.ts(48,1): error TS2554: Expected 2 arguments, but got 0.
+tests/cases/conformance/es2020/es2020IntlAPIs.ts(49,1): error TS2554: Expected 2 arguments, but got 1.
+tests/cases/conformance/es2020/es2020IntlAPIs.ts(50,29): error TS2345: Argument of type '{}' is not assignable to parameter of type 'DisplayNamesOptions'.
+  Property 'type' is missing in type '{}' but required in type 'DisplayNamesOptions'.
 
 
-==== tests/cases/conformance/es2020/es2020IntlAPIs.ts (1 errors) ====
+==== tests/cases/conformance/es2020/es2020IntlAPIs.ts (4 errors) ====
     // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#Locale_identification_and_negotiation
     const count = 26254.39;
     const date = new Date("2012-05-24");
@@ -50,4 +54,25 @@ tests/cases/conformance/es2020/es2020IntlAPIs.ts(45,1): error TS2554: Expected 1
     ~~~~~~~~~~~~~~~~~
 !!! error TS2554: Expected 1-2 arguments, but got 0.
 !!! related TS6210 /.ts/lib.es2020.intl.d.ts:311:14: An argument for 'tag' was not provided.
-    new Intl.Locale(new Intl.Locale('en-US'));
\ No newline at end of file
+    new Intl.Locale(new Intl.Locale('en-US'));
+    
+    new Intl.DisplayNames(); // TypeError: invalid_argument
+    ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2554: Expected 2 arguments, but got 0.
+!!! related TS6210 /.ts/lib.es2020.intl.d.ts:390:13: An argument for 'locales' was not provided.
+    new Intl.DisplayNames('en'); // TypeError: invalid_argument
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2554: Expected 2 arguments, but got 1.
+!!! related TS6210 /.ts/lib.es2020.intl.d.ts:390:39: An argument for 'options' was not provided.
+    new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+                                ~~
+!!! error TS2345: Argument of type '{}' is not assignable to parameter of type 'DisplayNamesOptions'.
+!!! error TS2345:   Property 'type' is missing in type '{}' but required in type 'DisplayNamesOptions'.
+!!! related TS2728 /.ts/lib.es2020.intl.d.ts:333:9: 'type' is declared here.
+    
+    const localesArg = ["es-ES", new Intl.Locale("en-US")];
+    console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"
+    console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-US"]
+    console.log(Intl.DisplayNames.supportedLocalesOf()); // []
+    console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})); // ["es-ES", "en-US"]
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/es2020IntlAPIs.js b/tests/baselines/reference/es2020IntlAPIs.js
index d08c2f427cdee..06b7f5577b1d0 100644
--- a/tests/baselines/reference/es2020IntlAPIs.js
+++ b/tests/baselines/reference/es2020IntlAPIs.js
@@ -44,7 +44,18 @@ const options1 = { localeMatcher: 'lookup' } as const;
 console.log(Intl.DisplayNames.supportedLocalesOf(locales1, options1).join(', '));
 
 new Intl.Locale(); // should error
-new Intl.Locale(new Intl.Locale('en-US'));
+new Intl.Locale(new Intl.Locale('en-US'));
+
+new Intl.DisplayNames(); // TypeError: invalid_argument
+new Intl.DisplayNames('en'); // TypeError: invalid_argument
+new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+
+const localesArg = ["es-ES", new Intl.Locale("en-US")];
+console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-US"]
+console.log(Intl.DisplayNames.supportedLocalesOf()); // []
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})); // ["es-ES", "en-US"]
+
 
 //// [es2020IntlAPIs.js]
 // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#Locale_identification_and_negotiation
@@ -78,3 +89,11 @@ const options1 = { localeMatcher: 'lookup' };
 console.log(Intl.DisplayNames.supportedLocalesOf(locales1, options1).join(', '));
 new Intl.Locale(); // should error
 new Intl.Locale(new Intl.Locale('en-US'));
+new Intl.DisplayNames(); // TypeError: invalid_argument
+new Intl.DisplayNames('en'); // TypeError: invalid_argument
+new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+const localesArg = ["es-ES", new Intl.Locale("en-US")];
+console.log((new Intl.DisplayNames(localesArg, { type: 'language' })).resolvedOptions().locale); // "es-ES"
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-US"]
+console.log(Intl.DisplayNames.supportedLocalesOf()); // []
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})); // ["es-ES", "en-US"]
diff --git a/tests/baselines/reference/es2020IntlAPIs.symbols b/tests/baselines/reference/es2020IntlAPIs.symbols
index 08986c4bf7d44..d4f2a2d41379b 100644
--- a/tests/baselines/reference/es2020IntlAPIs.symbols
+++ b/tests/baselines/reference/es2020IntlAPIs.symbols
@@ -160,3 +160,70 @@ new Intl.Locale(new Intl.Locale('en-US'));
 >Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >Locale : Symbol(Intl.Locale, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 
+new Intl.DisplayNames(); // TypeError: invalid_argument
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+
+new Intl.DisplayNames('en'); // TypeError: invalid_argument
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+
+new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+
+const localesArg = ["es-ES", new Intl.Locale("en-US")];
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
+>Intl.Locale : Symbol(Intl.Locale, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Locale : Symbol(Intl.Locale, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+
+console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>(new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale : Symbol(Intl.ResolvedDisplayNamesOptions.locale, Decl(lib.es2020.intl.d.ts, --, --))
+>(new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions : Symbol(Intl.DisplayNames.resolvedOptions, Decl(lib.es2020.intl.d.ts, --, --))
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
+>type : Symbol(type, Decl(es2020IntlAPIs.ts, 52, 48))
+>resolvedOptions : Symbol(Intl.DisplayNames.resolvedOptions, Decl(lib.es2020.intl.d.ts, --, --))
+>locale : Symbol(Intl.ResolvedDisplayNamesOptions.locale, Decl(lib.es2020.intl.d.ts, --, --))
+
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-US"]
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>Intl.DisplayNames.supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
+
+console.log(Intl.DisplayNames.supportedLocalesOf()); // []
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>Intl.DisplayNames.supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
+
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})); // ["es-ES", "en-US"]
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>Intl.DisplayNames.supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
+
diff --git a/tests/baselines/reference/es2020IntlAPIs.types b/tests/baselines/reference/es2020IntlAPIs.types
index 8cc08f6d8df19..b2f86fac9ad97 100644
--- a/tests/baselines/reference/es2020IntlAPIs.types
+++ b/tests/baselines/reference/es2020IntlAPIs.types
@@ -224,3 +224,93 @@ new Intl.Locale(new Intl.Locale('en-US'));
 >Locale : new (tag: string | Intl.Locale, options?: Intl.LocaleOptions) => Intl.Locale
 >'en-US' : "en-US"
 
+new Intl.DisplayNames(); // TypeError: invalid_argument
+>new Intl.DisplayNames() : Intl.DisplayNames
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+
+new Intl.DisplayNames('en'); // TypeError: invalid_argument
+>new Intl.DisplayNames('en') : Intl.DisplayNames
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>'en' : "en"
+
+new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+>new Intl.DisplayNames('en', {}) : Intl.DisplayNames
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>'en' : "en"
+>{} : {}
+
+const localesArg = ["es-ES", new Intl.Locale("en-US")];
+>localesArg : (string | Intl.Locale)[]
+>["es-ES", new Intl.Locale("en-US")] : (string | Intl.Locale)[]
+>"es-ES" : "es-ES"
+>new Intl.Locale("en-US") : Intl.Locale
+>Intl.Locale : new (tag: string | Intl.Locale, options?: Intl.LocaleOptions) => Intl.Locale
+>Intl : typeof Intl
+>Locale : new (tag: string | Intl.Locale, options?: Intl.LocaleOptions) => Intl.Locale
+>"en-US" : "en-US"
+
+console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"
+>console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale) : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>(new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale : string
+>(new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions() : Intl.ResolvedDisplayNamesOptions
+>(new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions : () => Intl.ResolvedDisplayNamesOptions
+>(new Intl.DisplayNames(localesArg, {type: 'language'})) : Intl.DisplayNames
+>new Intl.DisplayNames(localesArg, {type: 'language'}) : Intl.DisplayNames
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>localesArg : (string | Intl.Locale)[]
+>{type: 'language'} : { type: "language"; }
+>type : "language"
+>'language' : "language"
+>resolvedOptions : () => Intl.ResolvedDisplayNamesOptions
+>locale : string
+
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-US"]
+>console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)) : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>Intl.DisplayNames.supportedLocalesOf(localesArg) : string[]
+>Intl.DisplayNames.supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+>localesArg : (string | Intl.Locale)[]
+
+console.log(Intl.DisplayNames.supportedLocalesOf()); // []
+>console.log(Intl.DisplayNames.supportedLocalesOf()) : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>Intl.DisplayNames.supportedLocalesOf() : string[]
+>Intl.DisplayNames.supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})); // ["es-ES", "en-US"]
+>console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})) : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>Intl.DisplayNames.supportedLocalesOf(localesArg, {}) : string[]
+>Intl.DisplayNames.supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>supportedLocalesOf : (locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }) => string[]
+>localesArg : (string | Intl.Locale)[]
+>{} : {}
+
diff --git a/tests/cases/conformance/es2020/es2020IntlAPIs.ts b/tests/cases/conformance/es2020/es2020IntlAPIs.ts
index 70c52a0de3d3f..d9b4df620bee7 100644
--- a/tests/cases/conformance/es2020/es2020IntlAPIs.ts
+++ b/tests/cases/conformance/es2020/es2020IntlAPIs.ts
@@ -45,4 +45,14 @@ const options1 = { localeMatcher: 'lookup' } as const;
 console.log(Intl.DisplayNames.supportedLocalesOf(locales1, options1).join(', '));
 
 new Intl.Locale(); // should error
-new Intl.Locale(new Intl.Locale('en-US'));
\ No newline at end of file
+new Intl.Locale(new Intl.Locale('en-US'));
+
+new Intl.DisplayNames(); // TypeError: invalid_argument
+new Intl.DisplayNames('en'); // TypeError: invalid_argument
+new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+
+const localesArg = ["es-ES", new Intl.Locale("en-US")];
+console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-US"]
+console.log(Intl.DisplayNames.supportedLocalesOf()); // []
+console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})); // ["es-ES", "en-US"]

From d1c4a020414d9a18315393085b8d6e167248b36c Mon Sep 17 00:00:00 2001
From: jihndai <73680880+jihndai@users.noreply.github.com>
Date: Sat, 26 Mar 2022 19:33:03 -0400
Subject: [PATCH 4/4] add another test

---
 .../reference/es2020IntlAPIs.errors.txt       |  1 +
 tests/baselines/reference/es2020IntlAPIs.js   |  2 ++
 .../reference/es2020IntlAPIs.symbols          | 22 ++++++++++++++-----
 .../baselines/reference/es2020IntlAPIs.types  | 19 ++++++++++++++++
 .../conformance/es2020/es2020IntlAPIs.ts      |  1 +
 5 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/tests/baselines/reference/es2020IntlAPIs.errors.txt b/tests/baselines/reference/es2020IntlAPIs.errors.txt
index 4508afc98aaf4..95b447d43f170 100644
--- a/tests/baselines/reference/es2020IntlAPIs.errors.txt
+++ b/tests/baselines/reference/es2020IntlAPIs.errors.txt
@@ -69,6 +69,7 @@ tests/cases/conformance/es2020/es2020IntlAPIs.ts(50,29): error TS2345: Argument
 !!! error TS2345: Argument of type '{}' is not assignable to parameter of type 'DisplayNamesOptions'.
 !!! error TS2345:   Property 'type' is missing in type '{}' but required in type 'DisplayNamesOptions'.
 !!! related TS2728 /.ts/lib.es2020.intl.d.ts:333:9: 'type' is declared here.
+    console.log((new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB')); // "British English"
     
     const localesArg = ["es-ES", new Intl.Locale("en-US")];
     console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"
diff --git a/tests/baselines/reference/es2020IntlAPIs.js b/tests/baselines/reference/es2020IntlAPIs.js
index 06b7f5577b1d0..f440684ea2217 100644
--- a/tests/baselines/reference/es2020IntlAPIs.js
+++ b/tests/baselines/reference/es2020IntlAPIs.js
@@ -49,6 +49,7 @@ new Intl.Locale(new Intl.Locale('en-US'));
 new Intl.DisplayNames(); // TypeError: invalid_argument
 new Intl.DisplayNames('en'); // TypeError: invalid_argument
 new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+console.log((new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB')); // "British English"
 
 const localesArg = ["es-ES", new Intl.Locale("en-US")];
 console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"
@@ -92,6 +93,7 @@ new Intl.Locale(new Intl.Locale('en-US'));
 new Intl.DisplayNames(); // TypeError: invalid_argument
 new Intl.DisplayNames('en'); // TypeError: invalid_argument
 new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+console.log((new Intl.DisplayNames(undefined, { type: 'language' })).of('en-GB')); // "British English"
 const localesArg = ["es-ES", new Intl.Locale("en-US")];
 console.log((new Intl.DisplayNames(localesArg, { type: 'language' })).resolvedOptions().locale); // "es-ES"
 console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-US"]
diff --git a/tests/baselines/reference/es2020IntlAPIs.symbols b/tests/baselines/reference/es2020IntlAPIs.symbols
index d4f2a2d41379b..cb66c05131001 100644
--- a/tests/baselines/reference/es2020IntlAPIs.symbols
+++ b/tests/baselines/reference/es2020IntlAPIs.symbols
@@ -175,8 +175,20 @@ new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
 >Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 
+console.log((new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB')); // "British English"
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>(new Intl.DisplayNames(undefined, {type: 'language'})).of : Symbol(Intl.DisplayNames.of, Decl(lib.es2020.intl.d.ts, --, --))
+>Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>undefined : Symbol(undefined)
+>type : Symbol(type, Decl(es2020IntlAPIs.ts, 50, 47))
+>of : Symbol(Intl.DisplayNames.of, Decl(lib.es2020.intl.d.ts, --, --))
+
 const localesArg = ["es-ES", new Intl.Locale("en-US")];
->localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 52, 5))
 >Intl.Locale : Symbol(Intl.Locale, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >Locale : Symbol(Intl.Locale, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
@@ -190,8 +202,8 @@ console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOpti
 >Intl.DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
->localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
->type : Symbol(type, Decl(es2020IntlAPIs.ts, 52, 48))
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 52, 5))
+>type : Symbol(type, Decl(es2020IntlAPIs.ts, 53, 48))
 >resolvedOptions : Symbol(Intl.DisplayNames.resolvedOptions, Decl(lib.es2020.intl.d.ts, --, --))
 >locale : Symbol(Intl.ResolvedDisplayNamesOptions.locale, Decl(lib.es2020.intl.d.ts, --, --))
 
@@ -204,7 +216,7 @@ console.log(Intl.DisplayNames.supportedLocalesOf(localesArg)); // ["es-ES", "en-
 >Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
->localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 52, 5))
 
 console.log(Intl.DisplayNames.supportedLocalesOf()); // []
 >console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
@@ -225,5 +237,5 @@ console.log(Intl.DisplayNames.supportedLocalesOf(localesArg, {})); // ["es-ES",
 >Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2017.intl.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >DisplayNames : Symbol(Intl.DisplayNames, Decl(lib.es2020.intl.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
 >supportedLocalesOf : Symbol(supportedLocalesOf, Decl(lib.es2020.intl.d.ts, --, --))
->localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 51, 5))
+>localesArg : Symbol(localesArg, Decl(es2020IntlAPIs.ts, 52, 5))
 
diff --git a/tests/baselines/reference/es2020IntlAPIs.types b/tests/baselines/reference/es2020IntlAPIs.types
index b2f86fac9ad97..6014acbd0597b 100644
--- a/tests/baselines/reference/es2020IntlAPIs.types
+++ b/tests/baselines/reference/es2020IntlAPIs.types
@@ -245,6 +245,25 @@ new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
 >'en' : "en"
 >{} : {}
 
+console.log((new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB')); // "British English"
+>console.log((new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB')) : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>(new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB') : string
+>(new Intl.DisplayNames(undefined, {type: 'language'})).of : (code: string) => string
+>(new Intl.DisplayNames(undefined, {type: 'language'})) : Intl.DisplayNames
+>new Intl.DisplayNames(undefined, {type: 'language'}) : Intl.DisplayNames
+>Intl.DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>Intl : typeof Intl
+>DisplayNames : { new (locales: Intl.LocalesArgument, options: Intl.DisplayNamesOptions): Intl.DisplayNames; prototype: Intl.DisplayNames; supportedLocalesOf(locales?: Intl.LocalesArgument, options?: { localeMatcher?: Intl.RelativeTimeFormatLocaleMatcher; }): string[]; }
+>undefined : undefined
+>{type: 'language'} : { type: "language"; }
+>type : "language"
+>'language' : "language"
+>of : (code: string) => string
+>'en-GB' : "en-GB"
+
 const localesArg = ["es-ES", new Intl.Locale("en-US")];
 >localesArg : (string | Intl.Locale)[]
 >["es-ES", new Intl.Locale("en-US")] : (string | Intl.Locale)[]
diff --git a/tests/cases/conformance/es2020/es2020IntlAPIs.ts b/tests/cases/conformance/es2020/es2020IntlAPIs.ts
index d9b4df620bee7..e9687257bfe01 100644
--- a/tests/cases/conformance/es2020/es2020IntlAPIs.ts
+++ b/tests/cases/conformance/es2020/es2020IntlAPIs.ts
@@ -50,6 +50,7 @@ new Intl.Locale(new Intl.Locale('en-US'));
 new Intl.DisplayNames(); // TypeError: invalid_argument
 new Intl.DisplayNames('en'); // TypeError: invalid_argument
 new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
+console.log((new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB')); // "British English"
 
 const localesArg = ["es-ES", new Intl.Locale("en-US")];
 console.log((new Intl.DisplayNames(localesArg, {type: 'language'})).resolvedOptions().locale); // "es-ES"