ES6: Implement WeakMap and WeakSet constructor logic

src/weak_collection.js

Index: src/weak_collection.js
diff --git a/src/weak_collection.js b/src/weak_collection.js
index d9666ca12850c222e62a930c9f03c64c1098cb37..73dd9de6ba9aa5c48d16596ffde2c015e1764673 100644
--- a/src/weak_collection.js
+++ b/src/weak_collection.js
@@ -15,12 +15,36 @@ var $WeakSet = global.WeakSet;
 // -------------------------------------------------------------------
 // Harmony WeakMap
 
-function WeakMapConstructor() {
-  if (%_IsConstructCall()) {
-    %WeakCollectionInitialize(this);
-  } else {
+function WeakMapConstructor(iterable) {
+  if (!%_IsConstructCall()) {
     throw MakeTypeError('constructor_not_function', ['WeakMap']);
   }
+
+  var iter, adder;
+
+  if (!IS_NULL_OR_UNDEFINED(iterable)) {
+    iter = GetIterator(iterable);
+    adder = this.set;
+    if (!IS_SPEC_FUNCTION(adder)) {
+      throw MakeTypeError('property_not_function', ['set', this]);
+    }
+  }
+
+  %WeakCollectionInitialize(this);
+
+  if (IS_UNDEFINED(iter)) return;
+
+  var next, done, nextItem;
+  while (!(next = iter.next()).done) {
+    if (!IS_SPEC_OBJECT(next)) {
+      throw MakeTypeError('iterator_result_not_an_object', [next]);
+    }
+    nextItem = next.value;
+    if (!IS_SPEC_OBJECT(nextItem)) {
+      throw MakeTypeError('iterator_value_not_an_object', [nextItem]);
+    }
+    %_CallFunction(this, nextItem[0], nextItem[1], adder);
+  }
 }
 
 
@@ -107,12 +131,32 @@ SetUpWeakMap();
 // -------------------------------------------------------------------
 // Harmony WeakSet
 
-function WeakSetConstructor() {
-  if (%_IsConstructCall()) {
-    %WeakCollectionInitialize(this);
-  } else {
+function WeakSetConstructor(iterable) {
+  if (!%_IsConstructCall()) {
     throw MakeTypeError('constructor_not_function', ['WeakSet']);
   }
+
+  var iter, adder;
+
+  if (!IS_NULL_OR_UNDEFINED(iterable)) {
+    iter = GetIterator(iterable);
+    adder = this.add;
+    if (!IS_SPEC_FUNCTION(adder)) {
+      throw MakeTypeError('property_not_function', ['add', this]);
+    }
+  }
+
+  %WeakCollectionInitialize(this);
+
+  if (IS_UNDEFINED(iter)) return;
+
+  var next, done;
+  while (!(next = iter.next()).done) {
+    if (!IS_SPEC_OBJECT(next)) {
+      throw MakeTypeError('iterator_result_not_an_object', [next]);
+    }
+    %_CallFunction(this, next.value, adder);
+  }
 }