Version 3.6.5

src/proxy.js

Index: src/proxy.js
===================================================================
--- src/proxy.js	(revision 9531)
+++ src/proxy.js	(working copy)
@@ -41,14 +41,20 @@
     throw MakeTypeError("handler_non_object", ["create"])
   if (!IS_SPEC_FUNCTION(callTrap))
     throw MakeTypeError("trap_function_expected", ["createFunction", "call"])
+  var construct
   if (IS_UNDEFINED(constructTrap)) {
-    constructTrap = callTrap
-  } else if (!IS_SPEC_FUNCTION(constructTrap)) {
+    construct = DerivedConstructTrap(callTrap)
+  } else if (IS_SPEC_FUNCTION(constructTrap)) {
+    construct = function() {
+      // Make sure the trap receives 'undefined' as this.
+      return %Apply(constructTrap, void 0, arguments, 0, %_ArgumentsLength());
+    }
+  } else {
     throw MakeTypeError("trap_function_expected",
                         ["createFunction", "construct"])
   }
   return %CreateJSFunctionProxy(
-    handler, callTrap, constructTrap, $Function.prototype)
+    handler, callTrap, construct, $Function.prototype)
 }
 
 
@@ -57,6 +63,17 @@
 // Builtins
 ////////////////////////////////////////////////////////////////////////////////
 
+function DerivedConstructTrap(callTrap) {
+  return function() {
+    var proto = this.prototype
+    if (!IS_SPEC_OBJECT(proto)) proto = $Object.prototype
+    var obj = new $Object()
+    obj.__proto__ = proto
+    var result = %Apply(callTrap, obj, arguments, 0, %_ArgumentsLength());
+    return IS_SPEC_OBJECT(result) ? result : obj
+  }
+}
+
 function DelegateCallAndConstruct(callTrap, constructTrap) {
   return function() {
     return %Apply(%_IsConstructCall() ? constructTrap : callTrap,