Temporal dead zone behaviour for let bindings.

src/contexts.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 69 matching lines @@
 }
 
 void Context::set_global_proxy(JSObject* object) {
   global_context()->set_global_proxy_object(object);
 }
 
 
 Handle<Object> Context::Lookup(Handle<String> name,
                                ContextLookupFlags flags,
                                int* index_,
-                               PropertyAttributes* attributes) {
+                               PropertyAttributes* attributes,
+                               BindingFlags* binding_flags) {
   Isolate* isolate = GetIsolate();
   Handle<Context> context(this, isolate);
 
   bool follow_context_chain = (flags & FOLLOW_CONTEXT_CHAIN) != 0;
   *index_ = -1;
   *attributes = ABSENT;
 

[fschneider, 2011/08/23 08:36:12]

It's not so ideal to have the output parameter binding_flags uninitialized on
some paths. I'd also initialize binding_flags to a default value as it is done
for the other two parameters index and attributes.

[Steven, 2011/08/23 12:35:44]

Done.

   if (FLAG_trace_contexts) {
     PrintF("Context::Lookup(");
     name->ShortPrint();
     PrintF(")\n");
   }
 
   do {
     if (FLAG_trace_contexts) {
       PrintF(" - looking in context %p", reinterpret_cast<void*>(*context));
       if (context->IsGlobalContext()) PrintF(" (global context)");
       PrintF("\n");
     }
 
     // Check extension/with/global object.
     if (!context->IsBlockContext() && context->has_extension()) {
       if (context->IsCatchContext()) {
         // Catch contexts have the variable name in the extension slot.
         if (name->Equals(String::cast(context->extension()))) {
           if (FLAG_trace_contexts) {
             PrintF("=> found in catch context\n");
           }
           *index_ = Context::THROWN_OBJECT_INDEX;
           *attributes = NONE;
+          *binding_flags = MUTABLE_IS_INITIALIZED;
           return context;
         }
       } else {
         ASSERT(context->IsGlobalContext() ||
                context->IsFunctionContext() ||
                context->IsWithContext());
         // Global, function, and with contexts may have an object in the
         // extension slot.
         Handle<JSObject> extension(JSObject::cast(context->extension()),
                                    isolate);
@@ skipping 42 matching lines @@
         *index_ = index;
         // Note: Fixed context slots are statically allocated by the compiler.
         // Statically allocated variables always have a statically known mode,
         // which is the mode with which they were declared when added to the
         // scope. Thus, the DYNAMIC mode (which corresponds to dynamically
         // declared variables that were introduced through declaration nodes)
         // must not appear here.
         switch (mode) {
           case Variable::INTERNAL:  // Fall through.
           case Variable::VAR:
+            *attributes = NONE;
+            *binding_flags = MUTABLE_IS_INITIALIZED;
+            break;
           case Variable::LET:
             *attributes = NONE;
+            *binding_flags = MUTABLE_CHECK_INITIALIZED;
             break;
           case Variable::CONST:
             *attributes = READ_ONLY;
+            *binding_flags = IMMUTABLE_CHECK_INITIALIZED;
             break;
           case Variable::DYNAMIC:
           case Variable::DYNAMIC_GLOBAL:
           case Variable::DYNAMIC_LOCAL:
           case Variable::TEMPORARY:
             UNREACHABLE();
             break;
         }
         return context;
       }
 
       // Check the slot corresponding to the intermediate context holding
       // only the function name variable.
       if (follow_context_chain) {
         int index = scope_info->FunctionContextSlotIndex(*name);
         if (index >= 0) {
           if (FLAG_trace_contexts) {
             PrintF("=> found intermediate function in context slot %d\n",
                    index);
           }
           *index_ = index;
           *attributes = READ_ONLY;
+          *binding_flags = IMMUTABLE_IS_INITIALIZED;
           return context;
         }
       }
     }
 
     // Proceed with the previous context.
     if (context->IsGlobalContext()) {
       follow_context_chain = false;
     } else {
       context = Handle<Context>(context->previous(), isolate);
@@ skipping 144 matching lines @@
   // During bootstrapping we allow all objects to pass as global
   // objects. This is necessary to fix circular dependencies.
   Isolate* isolate = Isolate::Current();
   return isolate->heap()->gc_state() != Heap::NOT_IN_GC ||
       isolate->bootstrapper()->IsActive() ||
       object->IsGlobalObject();
 }
 #endif
 
 } }  // namespace v8::internal