filter cross context eval

src/generator.js

Index: src/generator.js
diff --git a/src/generator.js b/src/generator.js
index c152e3a6eea369d4c4306bb946df2d5edeeed29e..1ca3fd434d6cb6ba4afeeada4d7b9d1885acdab6 100644
--- a/src/generator.js
+++ b/src/generator.js
@@ -43,7 +43,9 @@ function GeneratorFunctionConstructor(arg1) {  // length == 1
   var global_receiver = %GlobalReceiver(global);
   // Compile the string in the constructor and not a helper so that errors
   // appear to come from here.
-  var f = %_CallFunction(global_receiver, %CompileString(source, true));
+  var f = %CompileString(source, true);
+  if (!IS_FUNCTION(f)) return f;
+  f = %_CallFunction(global_receiver, f);
   %FunctionMarkNameShouldPrintAsAnonymous(f);
   return f;
 }