Intl sub-classing is now restricted to class syntax.

test/intl402/10.1.2_a.js

@@ -15,14 +15,13 @@ var a = ["A", "C", "E", "B", "D", "F"];
 var referenceCollator = new Intl.Collator(locales);
 var referenceSorted = a.slice().sort(referenceCollator.compare);
 
-function MyCollator(locales, options) {
+class MyCollator extends Intl.Collator {
-    Intl.Collator.call(this, locales, options);
+  constructor(locales, options) {
+    super(locales, options);
     // could initialize MyCollator properties
   }
-
-MyCollator.prototype = Object.create(Intl.Collator.prototype);
-MyCollator.prototype.constructor = MyCollator;
   // could add methods to MyCollator.prototype
+}
 
 var collator = new MyCollator(locales);
 a.sort(collator.compare);

test/intl402/11.1.2.js

@@ -15,14 +15,13 @@ var a = [0, 1, -1, -123456.789, -Infinity, NaN];
 var referenceNumberFormat = new Intl.NumberFormat(locales);
 var referenceFormatted = a.map(referenceNumberFormat.format);
 
-function MyNumberFormat(locales, options) {
+class MyNumberFormat extends Intl.NumberFormat {
-    Intl.NumberFormat.call(this, locales, options);
+  constructor(locales, options) {
+    super(locales, options);
     // could initialize MyNumberFormat properties
   }
-
-MyNumberFormat.prototype = Object.create(Intl.NumberFormat.prototype);
-MyNumberFormat.prototype.constructor = MyNumberFormat;
   // could add methods to MyNumberFormat.prototype
+}
 
 var format = new MyNumberFormat(locales);
 var actual = a.map(format.format);

test/intl402/12.1.2.js

@@ -15,14 +15,13 @@ var a = [new Date(0), Date.now(), new Date(Date.parse("1989-11-09T17:57:00Z"))];
 var referenceDateTimeFormat = new Intl.DateTimeFormat(locales);
 var referenceFormatted = a.map(referenceDateTimeFormat.format);
 
-function MyDateTimeFormat(locales, options) {
+class MyDateTimeFormat extends Intl.DateTimeFormat {
-    Intl.DateTimeFormat.call(this, locales, options);
+  constructor(locales, options) {
+    super(locales, options);
     // could initialize MyDateTimeFormat properties
   }
-
-MyDateTimeFormat.prototype = Object.create(Intl.DateTimeFormat.prototype);
-MyDateTimeFormat.prototype.constructor = MyDateTimeFormat;
   // could add methods to MyDateTimeFormat.prototype
+}
 
 var format = new MyDateTimeFormat(locales);
 var actual = a.map(format.format);