[proxies] Implement [[Enumerate]] and [[OwnPropertyKeys]]

src/js/proxy.js

Index: src/js/proxy.js
diff --git a/src/js/proxy.js b/src/js/proxy.js
index 3885e408add350acff7d74276a48a28f7eb8cb5c..d1202f7066bd2d66170f7518f0b95376fb77807a 100644
--- a/src/js/proxy.js
+++ b/src/js/proxy.js
@@ -152,31 +152,30 @@ function DerivedKeysTrap() {
   return enumerableNames
 }
 
-function DerivedEnumerateTrap() {
-  var names = this.getPropertyNames()
-  var enumerableNames = []
-  for (var i = 0, count = 0; i < names.length; ++i) {
-    var name = names[i]
-    if (IS_SYMBOL(name)) continue
-    var desc = this.getPropertyDescriptor(TO_STRING(name))
-    if (!IS_UNDEFINED(desc)) {
-      if (!desc.configurable) {
-        throw MakeTypeError(kProxyPropNotConfigurable,
-                            this, name, "getPropertyDescriptor")
-      }
-      if (desc.enumerable) enumerableNames[count++] = names[i]
-    }
+// Implements part of ES6 9.5.11 Proxy.[[Enumerate]]:
+// Call the trap, which should return an iterator, exhaust the iterator,
+// and return an array containing the values.
+function ProxyEnumerate(trap, handler, target) {
+  // 7. Let trapResult be ? Call(trap, handler, «target»).
+  var trap_result = %_Call(trap, handler, target);
+  // 8. If Type(trapResult) is not Object, throw a TypeError exception.
+  if (!IS_SPEC_OBJECT(trap_result)) {
+    throw MakeTypeError(kProxyHandlerReturned, handler, "non-Object",
+                        "enumerate");
   }
-  return enumerableNames
-}
-
-function ProxyEnumerate(proxy) {
-  var handler = %GetHandler(proxy)
-  if (IS_UNDEFINED(handler.enumerate)) {
-    return %Apply(DerivedEnumerateTrap, handler, [], 0, 0)
-  } else {
-    return ToNameArray(handler.enumerate(), "enumerate", false)
+  // 9. Return trapResult.
+  var result = [];
+  for (var it = trap_result.next(); !it.done; it = trap_result.next()) {
+    var key = it.value;
+    // Not yet spec'ed as of 2015-11-25, but will be spec'ed soon:
+    // If the iterator returns a non-string value, throw a TypeError.
+    if (!IS_STRING(key)) {
+      throw MakeTypeError(kProxyHandlerReturned, handler, "non-String",
+                          "enumerate-iterator");
+    }
+    result.push(key);
   }
+  return result;
 }
 
 //-------------------------------------------------------------------