Avoid exposing compiler-allocated temporaries to the debugger

src/scopeinfo.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 260 matching lines @@
 
 
 InitializationFlag ScopeInfo::ContextLocalInitFlag(int var) {
   ASSERT(0 <= var && var < ContextLocalCount());
   int info_index = ContextLocalInfoEntriesIndex() + var;
   int value = Smi::cast(get(info_index))->value();
   return ContextLocalInitFlag::decode(value);
 }
 
 
+bool ScopeInfo::LocalIsSynthetic(int var) {
+  ASSERT(0 <= var && var < LocalCount());
+  // There's currently no flag stored on the ScopeInfo to indicate that a
+  // variable is a compiler-introduced temporary. However, to avoid conflict
+  // with user declarations, the current temporaries like .generator_object and
+  // .result start with a dot, so we can use that as a flag. It's a hack!
+  Handle<String> name(LocalName(var));
+  return name->length() > 0 && name->Get(0) == '.';
+}
+
+
 int ScopeInfo::StackSlotIndex(String* name) {
   ASSERT(name->IsInternalizedString());
   if (length() > 0) {
     int start = StackLocalEntriesIndex();
     int end = StackLocalEntriesIndex() + StackLocalCount();
     for (int i = start; i < end; ++i) {
       if (name == get(i)) {
         return i - start;
       }
     }
@@ skipping 70 matching lines @@
 }
 
 
 bool ScopeInfo::CopyContextLocalsToScopeObject(Handle<ScopeInfo> scope_info,
                                                Handle<Context> context,
                                                Handle<JSObject> scope_object) {
   Isolate* isolate = scope_info->GetIsolate();
   int local_count = scope_info->ContextLocalCount();
   if (local_count == 0) return true;
   // Fill all context locals to the context extension.
+  int first_context_var = scope_info->StackLocalCount();
   int start = scope_info->ContextLocalNameEntriesIndex();
-  int end = start + local_count;
-  for (int i = start; i < end; ++i) {
-    int context_index = Context::MIN_CONTEXT_SLOTS + i - start;
+  for (int i = 0; i < local_count; ++i) {
+    if (scope_info->LocalIsSynthetic(first_context_var + i)) continue;
+    int context_index = Context::MIN_CONTEXT_SLOTS + i;
     RETURN_ON_EXCEPTION_VALUE(
         isolate,
         Runtime::SetObjectProperty(
             isolate,
             scope_object,
-            Handle<String>(String::cast(scope_info->get(i))),
+            Handle<String>(String::cast(scope_info->get(i + start))),
             Handle<Object>(context->get(context_index), isolate),
             ::NONE,
             SLOPPY),
         false);
   }
   return true;
 }
 
 
 int ScopeInfo::ParameterEntriesIndex() {
@@ skipping 163 matching lines @@
     } else {
       ASSERT(var->index() >= 0);
       info->set_index(i, var->index());
     }
   }
   ASSERT(i == info->length());
   return info;
 }
 
 } }  // namespace v8::internal