Block scoped const variables.

src/runtime.cc

 // Copyright 2011 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 8802 matching lines @@
     ASSERT(holder->IsContext());
     // If the "property" we were looking for is a local variable, the
     // receiver is the global object; see ECMA-262, 3rd., 10.1.6 and 10.2.3.
     //
     // Use the hole as the receiver to signal that the receiver is implicit
     // and that the global receiver should be used (as distinguished from an
     // explicit receiver that happens to be a global object).
     Handle<Object> receiver = isolate->factory()->the_hole_value();
     Object* value = Context::cast(*holder)->get(index);
     // Check for uninitialized bindings.
-    if (binding_flags == MUTABLE_CHECK_INITIALIZED && value->IsTheHole()) {
-      Handle<Object> reference_error =
-          isolate->factory()->NewReferenceError("not_defined",
-                                                HandleVector(&name, 1));
-      return MakePair(isolate->Throw(*reference_error), NULL);
-    } else {
-      return MakePair(Unhole(isolate->heap(), value, attributes), *receiver);
+    switch (binding_flags) {
+      case MUTABLE_CHECK_INITIALIZED:
+      case IMMUTABLE_CHECK_INITIALIZED_HARMONY:
+        if (value->IsTheHole()) {
+          Handle<Object> reference_error =
+              isolate->factory()->NewReferenceError("not_defined",
+                                                    HandleVector(&name, 1));
+          return MakePair(isolate->Throw(*reference_error), NULL);
+        }
+        // FALLTHROUGH
+      case MUTABLE_IS_INITIALIZED:
+      case IMMUTABLE_IS_INITIALIZED:
+      case IMMUTABLE_IS_INITIALIZED_HARMONY:
+        ASSERT(!value->IsTheHole());
+        return MakePair(value, *receiver);
+      case IMMUTABLE_CHECK_INITIALIZED:
+        return MakePair(Unhole(isolate->heap(), value, attributes), *receiver);
+      case MISSING_BINDING:
+        UNREACHABLE();
     }
   }
 
   // Otherwise, if the slot was found the holder is a context extension
   // object, subject of a with, or a global object.  We read the named
   // property from it.
   if (!holder.is_null()) {
     Handle<JSObject> object = Handle<JSObject>::cast(holder);
     ASSERT(object->HasProperty(*name));
     // GetProperty below can cause GC.
@@ skipping 4506 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags);
   }
 }
 
 
 } }  // namespace v8::internal