Revert change to const and global variable declarations. It causes

src/runtime.cc

 // Copyright 2010 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 1033 matching lines @@
               const char* type = (is_read_only) ? "const" : "var";
               return ThrowRedeclarationError(type, name);
             };
             // The property already exists without conflicting: Go to
             // the next declaration.
             continue;
           }
           // Fall-through and introduce the absent property by using
           // SetProperty.
         } else {
-          // For const properties, we treat a callback with this name
-          // even in the prototype as a conflicting declaration.
-          if (is_const_property && (lookup.type() == CALLBACKS)) {
-            return ThrowRedeclarationError("const", name);
-          }
-          // Otherwise, we check for locally conflicting declarations.
           if (is_local && (is_read_only || is_const_property)) {
             const char* type = (is_read_only) ? "const" : "var";
             return ThrowRedeclarationError(type, name);
           }
           // The property already exists without conflicting: Go to
           // the next declaration.
           continue;
         }
       }
     } else {
       // Copy the function and update its context. Use it as value.
       Handle<SharedFunctionInfo> shared =
           Handle<SharedFunctionInfo>::cast(value);
       Handle<JSFunction> function =
           Factory::NewFunctionFromSharedFunctionInfo(shared, context, TENURED);
       value = function;
     }
 
     LookupResult lookup;
     global->LocalLookup(*name, &lookup);
 
     PropertyAttributes attributes = is_const_property
         ? static_cast<PropertyAttributes>(base | READ_ONLY)
         : base;
 
-    // There's a local property that we need to overwrite because
-    // we're either declaring a function or there's an interceptor
-    // that claims the property is absent.
-    //
-    // Check for conflicting re-declarations. We cannot have
-    // conflicting types in case of intercepted properties because
-    // they are absent.
-    if (lookup.IsProperty() &&
-        (lookup.type() != INTERCEPTOR) &&
-        (lookup.IsReadOnly() || is_const_property)) {
-      const char* type = (lookup.IsReadOnly()) ? "const" : "var";
-      return ThrowRedeclarationError(type, name);
+    if (lookup.IsProperty()) {
+      // There's a local property that we need to overwrite because
+      // we're either declaring a function or there's an interceptor
+      // that claims the property is absent.
+
+      // Check for conflicting re-declarations. We cannot have
+      // conflicting types in case of intercepted properties because
+      // they are absent.
+      if (lookup.type() != INTERCEPTOR &&
+          (lookup.IsReadOnly() || is_const_property)) {
+        const char* type = (lookup.IsReadOnly()) ? "const" : "var";
+        return ThrowRedeclarationError(type, name);
+      }
+      RETURN_IF_EMPTY_HANDLE(SetProperty(global, name, value, attributes));
+    } else {
+      // If a property with this name does not already exist on the
+      // global object add the property locally.  We take special
+      // precautions to always add it as a local property even in case
+      // of callbacks in the prototype chain (this rules out using
+      // SetProperty).  Also, we must use the handle-based version to
+      // avoid GC issues.
+      RETURN_IF_EMPTY_HANDLE(
+          SetLocalPropertyIgnoreAttributes(global, name, value, attributes));
     }
-    RETURN_IF_EMPTY_HANDLE(SetProperty(global, name, value, attributes));
   }
 
   ASSERT(!Top::has_pending_exception());
   return Heap::undefined_value();
 }
 
 
 static MaybeObject* Runtime_DeclareContextSlot(Arguments args) {
   HandleScope scope;
   ASSERT(args.length() == 4);
@@ skipping 66 matching lines @@
       context->set_extension(*context_ext);
     }
     ASSERT(*context_ext != NULL);
 
     // Declare the property by setting it to the initial value if provided,
     // or undefined, and use the correct mode (e.g. READ_ONLY attribute for
     // constant declarations).
     ASSERT(!context_ext->HasLocalProperty(*name));
     Handle<Object> value(Heap::undefined_value());
     if (*initial_value != NULL) value = initial_value;
-    // Declaring a const context slot is a conflicting declaration if
-    // there is a callback with that name in a prototype. It is
-    // allowed to introduce const variables in
-    // JSContextExtensionObjects. They are treated specially in
-    // SetProperty and no setters are invoked for those since they are
-    // not real JSObjects.
-    if (initial_value->IsTheHole() &&
-        !context_ext->IsJSContextExtensionObject()) {
-      LookupResult lookup;
-      context_ext->Lookup(*name, &lookup);
-      if (lookup.IsProperty() && (lookup.type() == CALLBACKS)) {
-        return ThrowRedeclarationError("const", name);
-      }
-    }
     RETURN_IF_EMPTY_HANDLE(SetProperty(context_ext, name, value, mode));
   }
 
   return Heap::undefined_value();
 }
 
 
 static MaybeObject* Runtime_InitializeVarGlobal(Arguments args) {
   NoHandleAllocation nha;
 
   // Determine if we need to assign to the variable if it already
   // exists (based on the number of arguments).
   RUNTIME_ASSERT(args.length() == 1 || args.length() == 2);
   bool assign = args.length() == 2;
 
   CONVERT_ARG_CHECKED(String, name, 0);
   GlobalObject* global = Top::context()->global();
 
   // According to ECMA-262, section 12.2, page 62, the property must
   // not be deletable.
   PropertyAttributes attributes = DONT_DELETE;
 
   // Lookup the property locally in the global object. If it isn't
   // there, there is a property with this name in the prototype chain.
   // We follow Safari and Firefox behavior and only set the property
   // locally if there is an explicit initialization value that we have
-  // to assign to the property.
+  // to assign to the property. When adding the property we take
+  // special precautions to always add it as a local property even in
+  // case of callbacks in the prototype chain (this rules out using
+  // SetProperty).  We have SetLocalPropertyIgnoreAttributes for
+  // this.
   // Note that objects can have hidden prototypes, so we need to traverse
   // the whole chain of hidden prototypes to do a 'local' lookup.
   JSObject* real_holder = global;
   LookupResult lookup;
   while (true) {
     real_holder->LocalLookup(*name, &lookup);
     if (lookup.IsProperty()) {
       // Determine if this is a redeclaration of something read-only.
       if (lookup.IsReadOnly()) {
         // If we found readonly property on one of hidden prototypes,
@@ skipping 40 matching lines @@
     if (!proto->IsJSObject())
       break;
 
     if (!JSObject::cast(proto)->map()->is_hidden_prototype())
       break;
 
     real_holder = JSObject::cast(proto);
   }
 
   global = Top::context()->global();
-  if (assign) return global->SetProperty(*name, args[1], attributes);
+  if (assign) {
+    return global->SetLocalPropertyIgnoreAttributes(*name,
+                                                    args[1],
+                                                    attributes);
+  }
   return Heap::undefined_value();
 }
 
 
 static MaybeObject* Runtime_InitializeConstGlobal(Arguments args) {
   // All constants are declared with an initial value. The name
   // of the constant is the first argument and the initial value
   // is the second.
   RUNTIME_ASSERT(args.length() == 2);
   CONVERT_ARG_CHECKED(String, name, 0);
@@ skipping 9906 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal