Array/TypedArray/ArrayBuffer method subclassing and @@species

src/js/runtime.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This files contains runtime support implemented in JavaScript.
 
 // CAUTION: Some of the functions specified in this file are called
 // directly from compiled code. These are the functions with names in
 // ALL CAPS. The compiled code passes the first argument in 'this'.
 
 
 // The following declarations are shared with other native JS files.
 // They are all declared at this one spot to avoid redeclaration errors.
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
+var FLAG_harmony_species;
 var GlobalArray = global.Array;
 var GlobalBoolean = global.Boolean;
 var GlobalString = global.String;
-var isConcatSpreadableSymbol =
-    utils.ImportNow("is_concat_spreadable_symbol");
 var MakeRangeError;
+var MakeTypeError;
+var speciesSymbol;
 
 utils.Import(function(from) {
   MakeRangeError = from.MakeRangeError;
+  MakeTypeError = from.MakeTypeError;
+  speciesSymbol = from.species_symbol;
+});
+
+utils.ImportFromExperimental(function(from) {
+  FLAG_harmony_species = from.FLAG_harmony_species;
 });
 
 // ----------------------------------------------------------------------------
 
 /* -----------------------------
    - - -   H e l p e r s   - - -
    -----------------------------
 */
 
 function CONCAT_ITERABLE_TO_ARRAY(iterable) {
@@ skipping 73 matching lines @@
 
 
 function MinSimple(a, b) {
   return a > b ? b : a;
 }
 
 
 %SetForceInlineFlag(MaxSimple);
 %SetForceInlineFlag(MinSimple);
 
+
+// ES2015 7.3.20
+function SpeciesConstructor(object, defaultConstructor) {
+  if (FLAG_harmony_species) {
+    var constructor = object.constructor;
+    if (IS_UNDEFINED(constructor)) {
+      return defaultConstructor;
+    }
+    if (!IS_RECEIVER(constructor)) {
+      throw MakeTypeError(kSpeciesNotConstructor);
+    }
+    var species = constructor[speciesSymbol];
+    if (IS_NULL_OR_UNDEFINED(species)) {
+      return defaultConstructor;
+    }
+    if (%IsConstructor(species)) {
+      return species;
+    }
+    throw MakeTypeError(kSpeciesNotConstructor);
+  } else {
+    return defaultConstructor;
+  }
+}
+
 //----------------------------------------------------------------------------
 
 // NOTE: Setting the prototype for Array must take place as early as
 // possible due to code generation for array literals.  When
 // generating code for a array literal a boilerplate array is created
 // that is cloned when running the code.  It is essential that the
 // boilerplate gets the right prototype.
 %FunctionSetPrototype(GlobalArray, new GlobalArray(0));
 
 // ----------------------------------------------------------------------------
 // Exports
 
 utils.Export(function(to) {
   to.AddIndexedProperty = AddIndexedProperty;
   to.MaxSimple = MaxSimple;
   to.MinSimple = MinSimple;
   to.SameValue = SameValue;
   to.SameValueZero = SameValueZero;
   to.ToPositiveInteger = ToPositiveInteger;
+  to.SpeciesConstructor = SpeciesConstructor;
 });
 
 %InstallToContext([
   "concat_iterable_to_array_builtin", CONCAT_ITERABLE_TO_ARRAY,
 ]);
 
 %InstallToContext([
   "concat_iterable_to_array", ConcatIterableToArray,
 ]);
 
 })