Add new semantics + compat fallback to Intl constructor

src/js/i18n.js

Index: src/js/i18n.js
diff --git a/src/js/i18n.js b/src/js/i18n.js
index cbb664b526973beb6bb7df7d1fc256b31a4e511d..78e2fb5492449978c469203b5370aba2d8794bbb 100644
--- a/src/js/i18n.js
+++ b/src/js/i18n.js
@@ -29,6 +29,7 @@ var GlobalDate = global.Date;
 var GlobalNumber = global.Number;
 var GlobalRegExp = global.RegExp;
 var GlobalString = global.String;
+var GlobalSymbol = global.Symbol;
 var MakeError;
 var MakeRangeError;
 var MakeTypeError;
@@ -84,31 +85,31 @@ function InstallConstructor(object, name, func) {
   %ToFastProperties(object);
 }
 
+var fallbackSymbol = GlobalSymbol("intl fallback");
+
 /**
  * Adds bound method to the prototype of the given object.
  */
-function AddBoundMethod(obj, methodName, implementation, length) {
+function AddBoundMethod(obj, methodName, implementation, length, typename, compat) {
   %CheckIsBootstrapping();
   var internalName = %CreatePrivateSymbol(methodName);
   var getter = function() {
-    if (!%IsInitializedIntlObject(this)) {
-      throw MakeTypeError(kMethodCalledOnWrongObject, methodName);
-    }
-    if (IS_UNDEFINED(this[internalName])) {
+    var receiver = Unwrap(this, typename, obj, methodName, compat);
+    if (IS_UNDEFINED(receiver[internalName])) {
       var boundMethod;
       if (IS_UNDEFINED(length) || length === 2) {
-        boundMethod = (x, y) => implementation(this, x, y);
+        boundMethod = (x, y) => implementation(receiver, x, y);
       } else if (length === 1) {
-        boundMethod = x => implementation(this, x);
+        boundMethod = x => implementation(receiver, x);
       } else {
         boundMethod = (...args) => {
           // DateTimeFormat.format needs to be 0 arg method, but can stil
           // receive optional dateValue param. If one was provided, pass it
           // along.
           if (args.length > 0) {
-            return implementation(this, args[0]);
+            return implementation(receiver, args[0]);
           } else {
-            return implementation(this);
+            return implementation(receiver);
           }
         }
       }
@@ -118,14 +119,51 @@ function AddBoundMethod(obj, methodName, implementation, length) {
       %FunctionSetName(boundMethod, '__bound' + methodName + '__');
       %FunctionRemovePrototype(boundMethod);
       %SetNativeFlag(boundMethod);
-      this[internalName] = boundMethod;
+      receiver[internalName] = boundMethod;
     }
-    return this[internalName];
+    return receiver[internalName];
   };
 
   InstallGetter(obj.prototype, methodName, getter, DONT_ENUM);
 }
 
+function IntlConstruct(receiver, constructor, initializer, newTarget, args,
+                       compat) {
+  var locales = args[0];
+  var options = args[1];
+
+  if (IS_UNDEFINED(newTarget)) {
+    if (compat && receiver instanceof constructor) {
+      let success = ObjectDefineProperty(receiver, fallbackSymbol,
+                           { value: new constructor(locales, options) });
+      if (!success) {
+        throw MakeTypeError(kReinitializeIntl, constructor);
+      }
+      return receiver;
+    }
+
+    return new constructor(locales, options);
+  }
+
+  return initializer(receiver, locales, options);
+}
+
+
+
+function Unwrap(receiver, typename, constructor, method, compat) {
+  if (!%IsInitializedIntlObjectOfType(receiver, typename)) {
+    if (compat && receiver instanceof constructor) {
+      let fallback = receiver[fallbackSymbol];
+      if (%IsInitializedIntlObjectOfType(fallback, typename)) {
+        return fallback;
+      }
+    }
+    throw MakeTypeError(kIncompatibleMethodReceiver, method, receiver);
+  }
+  return receiver;
+}
+
+
 // -------------------------------------------------------------------
 
 var Intl = {};
@@ -1002,18 +1040,11 @@ function initializeCollator(collator, locales, options) {
  *
  * @constructor
  */
-InstallConstructor(Intl, 'Collator', function() {
-    var locales = arguments[0];
-    var options = arguments[1];
-
-    if (!this || this === Intl) {
-      // Constructor is called as a function.
-      return new Intl.Collator(locales, options);
-    }
-
-    return initializeCollator(TO_OBJECT(this), locales, options);
-  }
-);
+function Collator() {
+  return IntlConstruct(this, Collator, initializeCollator, new.target,
+                       arguments);
+}
+InstallConstructor(Intl, 'Collator', Collator);
 
 
 /**
@@ -1024,11 +1055,7 @@ InstallFunction(Intl.Collator.prototype, 'resolvedOptions', function() {
       throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
     }
 
-    if (!%IsInitializedIntlObjectOfType(this, 'collator')) {
-      throw MakeTypeError(kResolvedOptionsCalledOnNonObject, "Collator");
-    }
-
-    var coll = this;
+    var coll = Unwrap(this, 'collator', Collator, 'resolvedOptions', true);
     var locale = getOptimalLanguageTag(coll[resolvedSymbol].requestedLocale,
                                        coll[resolvedSymbol].locale);
 
@@ -1077,7 +1104,7 @@ function compare(collator, x, y) {
 };
 
 
-AddBoundMethod(Intl.Collator, 'compare', compare, 2);
+AddBoundMethod(Intl.Collator, 'compare', compare, 2, 'collator', Collator);
 
 /**
  * Verifies that the input is a well-formed ISO 4217 currency code.
@@ -1246,18 +1273,11 @@ function initializeNumberFormat(numberFormat, locales, options) {
  *
  * @constructor
  */
-InstallConstructor(Intl, 'NumberFormat', function() {
-    var locales = arguments[0];
-    var options = arguments[1];
-
-    if (!this || this === Intl) {
-      // Constructor is called as a function.
-      return new Intl.NumberFormat(locales, options);
-    }
-
-    return initializeNumberFormat(TO_OBJECT(this), locales, options);
-  }
-);
+function NumberFormat() {
+  return IntlConstruct(this, NumberFormat, initializeNumberFormat, new.target,
+                       arguments, true);
+}
+InstallConstructor(Intl, 'NumberFormat', NumberFormat);
 
 
 /**
@@ -1268,11 +1288,8 @@ InstallFunction(Intl.NumberFormat.prototype, 'resolvedOptions', function() {
       throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
     }
 
-    if (!%IsInitializedIntlObjectOfType(this, 'numberformat')) {
-      throw MakeTypeError(kResolvedOptionsCalledOnNonObject, "NumberFormat");
-    }
-
-    var format = this;
+    var format = Unwrap(this, 'numberformat', NumberFormat,
+                        'resolvedOptions', true);
     var locale = getOptimalLanguageTag(format[resolvedSymbol].requestedLocale,
                                        format[resolvedSymbol].locale);
 
@@ -1346,8 +1363,8 @@ function parseNumber(formatter, value) {
 }
 
 
-AddBoundMethod(Intl.NumberFormat, 'format', formatNumber, 1);
-AddBoundMethod(Intl.NumberFormat, 'v8Parse', parseNumber, 1);
+AddBoundMethod(Intl.NumberFormat, 'format', formatNumber, 1, 'numberformat', true);
+AddBoundMethod(Intl.NumberFormat, 'v8Parse', parseNumber, 1, 'numberformat');
 
 /**
  * Returns a string that matches LDML representation of the options object.
@@ -1640,18 +1657,11 @@ function initializeDateTimeFormat(dateFormat, locales, options) {
  *
  * @constructor
  */
-InstallConstructor(Intl, 'DateTimeFormat', function() {
-    var locales = arguments[0];
-    var options = arguments[1];
-
-    if (!this || this === Intl) {
-      // Constructor is called as a function.
-      return new Intl.DateTimeFormat(locales, options);
-    }
-
-    return initializeDateTimeFormat(TO_OBJECT(this), locales, options);
-  }
-);
+function DateTimeFormat() {
+  return IntlConstruct(this, DateTimeFormat, initializeDateTimeFormat,
+                       new.target, arguments, true);
+}
+InstallConstructor(Intl, 'DateTimeFormat', DateTimeFormat);
 
 
 /**
@@ -1662,9 +1672,8 @@ InstallFunction(Intl.DateTimeFormat.prototype, 'resolvedOptions', function() {
       throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
     }
 
-    if (!%IsInitializedIntlObjectOfType(this, 'dateformat')) {
-      throw MakeTypeError(kResolvedOptionsCalledOnNonObject, "DateTimeFormat");
-    }
+    var format = Unwrap(this, 'dateformat', DateTimeFormat,
+                        'resolvedOptions', true);
 
     /**
      * Maps ICU calendar names into LDML type.
@@ -1769,8 +1778,8 @@ function parseDate(formatter, value) {
 
 
 // 0 because date is optional argument.
-AddBoundMethod(Intl.DateTimeFormat, 'format', formatDate, 0);
-AddBoundMethod(Intl.DateTimeFormat, 'v8Parse', parseDate, 1);
+AddBoundMethod(Intl.DateTimeFormat, 'format', formatDate, 0, 'dateformat', true);
+AddBoundMethod(Intl.DateTimeFormat, 'v8Parse', parseDate, 1, 'dateformat');
 
 
 /**
@@ -1857,18 +1866,11 @@ function initializeBreakIterator(iterator, locales, options) {
  *
  * @constructor
  */
-InstallConstructor(Intl, 'v8BreakIterator', function() {
-    var locales = arguments[0];
-    var options = arguments[1];
-
-    if (!this || this === Intl) {
-      // Constructor is called as a function.
-      return new Intl.v8BreakIterator(locales, options);
-    }
-
-    return initializeBreakIterator(TO_OBJECT(this), locales, options);
-  }
-);
+function v8BreakIterator() {
+  return IntlConstruct(this, v8BreakIterator, initializeBreakIterator,
+                       new.target, arguments);
+}
+InstallConstructor(Intl, 'v8BreakIterator', v8BreakIterator);
 
 
 /**
@@ -1880,9 +1882,7 @@ InstallFunction(Intl.v8BreakIterator.prototype, 'resolvedOptions',
       throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
     }
 
-    if (!%IsInitializedIntlObjectOfType(this, 'breakiterator')) {
-      throw MakeTypeError(kResolvedOptionsCalledOnNonObject, "v8BreakIterator");
-    }
+    var format = Unwrap(this, 'breakiterator', v8BreakIterator, 'resolvedOptions');
 
     var segmenter = this;
     var locale =
@@ -1956,11 +1956,11 @@ function breakType(iterator) {
 }
 
 
-AddBoundMethod(Intl.v8BreakIterator, 'adoptText', adoptText, 1);
-AddBoundMethod(Intl.v8BreakIterator, 'first', first, 0);
-AddBoundMethod(Intl.v8BreakIterator, 'next', next, 0);
-AddBoundMethod(Intl.v8BreakIterator, 'current', current, 0);
-AddBoundMethod(Intl.v8BreakIterator, 'breakType', breakType, 0);
+AddBoundMethod(Intl.v8BreakIterator, 'adoptText', adoptText, 1, 'breakiterator');
+AddBoundMethod(Intl.v8BreakIterator, 'first', first, 0, 'breakiterator');
+AddBoundMethod(Intl.v8BreakIterator, 'next', next, 0, 'breakiterator');
+AddBoundMethod(Intl.v8BreakIterator, 'current', current, 0, 'breakiterator');
+AddBoundMethod(Intl.v8BreakIterator, 'breakType', breakType, 0, 'breakiterator');
 
 // Save references to Intl objects and methods we use, for added security.
 var savedObjects = {