ES6: Map and Set needs to normalize minus zero

src/collection.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 22 matching lines @@
 
 var $Set = global.Set;
 var $Map = global.Map;
 var $WeakMap = global.WeakMap;
 var $WeakSet = global.WeakSet;
 
 // Global sentinel to be used instead of undefined keys, which are not
 // supported internally but required for Harmony sets and maps.
 var undefined_sentinel = {};
 
+
+// Map and Set uses SameValueZero which means that +0 and -0 should be treated
+// as the same value.
+function NormalizeKey(key) {
+  if (IS_UNDEFINED(key)) {
+    return undefined_sentinel;
+  }
+
+  if (key === 0) {
+    return 0;
+  }
+
+  return key;
+}
+
+
 // -------------------------------------------------------------------
 // Harmony Set
 
 function SetConstructor() {
   if (%_IsConstructCall()) {
     %SetInitialize(this);
   } else {
     throw MakeTypeError('constructor_not_function', ['Set']);
   }
 }
 
 
 function SetAdd(key) {
   if (!IS_SET(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Set.prototype.add', this]);
   }
-  if (IS_UNDEFINED(key)) {
-    key = undefined_sentinel;
-  }
-  return %SetAdd(this, key);
+  return %SetAdd(this, NormalizeKey(key));
 }
 
 
 function SetHas(key) {
   if (!IS_SET(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Set.prototype.has', this]);
   }
-  if (IS_UNDEFINED(key)) {
-    key = undefined_sentinel;
-  }
-  return %SetHas(this, key);
+  return %SetHas(this, NormalizeKey(key));
 }
 
 
 function SetDelete(key) {
   if (!IS_SET(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Set.prototype.delete', this]);
   }
-  if (IS_UNDEFINED(key)) {
-    key = undefined_sentinel;
-  }
+  key = NormalizeKey(key);
   if (%SetHas(this, key)) {
     %SetDelete(this, key);
     return true;
   } else {
     return false;
   }
 }
 
 
 function SetGetSize() {
@@ skipping 47 matching lines @@
     throw MakeTypeError('constructor_not_function', ['Map']);
   }
 }
 
 
 function MapGet(key) {
   if (!IS_MAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.get', this]);
   }
-  if (IS_UNDEFINED(key)) {
-    key = undefined_sentinel;
-  }
-  return %MapGet(this, key);
+  return %MapGet(this, NormalizeKey(key));
 }
 
 
 function MapSet(key, value) {
   if (!IS_MAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.set', this]);
   }
-  if (IS_UNDEFINED(key)) {
-    key = undefined_sentinel;
-  }
-  return %MapSet(this, key, value);
+  return %MapSet(this, NormalizeKey(key), value);
 }
 
 
 function MapHas(key) {
   if (!IS_MAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.has', this]);
   }
-  if (IS_UNDEFINED(key)) {
-    key = undefined_sentinel;
-  }
-  return %MapHas(this, key);
+  return %MapHas(this, NormalizeKey(key));
 }
 
 
 function MapDelete(key) {
   if (!IS_MAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.delete', this]);
   }
-  if (IS_UNDEFINED(key)) {
-    key = undefined_sentinel;
-  }
-  return %MapDelete(this, key);
+  return %MapDelete(this, NormalizeKey(key));
 }
 
 
 function MapGetSize() {
   if (!IS_MAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.size', this]);
   }
   return %MapGetSize(this);
 }
@@ skipping 194 matching lines @@
   // Set up the non-enumerable functions on the WeakSet prototype object.
   InstallFunctions($WeakSet.prototype, DONT_ENUM, $Array(
     "add", WeakSetAdd,
     "has", WeakSetHas,
     "delete", WeakSetDelete,
     "clear", WeakSetClear
   ));
 }
 
 SetUpWeakSet();