Reapply "Fix the ScopeIterator reimplementation".

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 43e1a6dee412df9dd8937638fec9cf2a8545a519..a2e569b31ece4a2cc41fe69e885154c6ad34bc49 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -11201,27 +11201,83 @@ class ScopeIterator {
       inlined_frame_index_(inlined_frame_index),
       function_(JSFunction::cast(frame->function())),
       context_(Context::cast(frame->context())),
-      local_done_(false),
-      at_local_(false) {
-
-    // Check whether the first scope is actually a local scope.
-    // If there is a stack slot for .result then this local scope has been
-    // created for evaluating top level code and it is not a real local scope.
-    // Checking for the existence of .result seems fragile, but the scope info
-    // saved with the code object does not otherwise have that information.
-    int index = function_->shared()->scope_info()->
-        StackSlotIndex(isolate_->heap()->result_symbol());
-    if (index >= 0) {
-      local_done_ = true;
-    } else if (context_->IsGlobalContext() ||
-               context_->IsFunctionContext()) {
-      at_local_ = true;
-    } else if (context_->closure() != *function_) {
-      // The context_ is a block or with or catch block from the outer function.
-      ASSERT(context_->IsWithContext() ||
-             context_->IsCatchContext() ||
-             context_->IsBlockContext());
-      at_local_ = true;
+      nested_scope_chain_(4) {
+
+    // Catch the case when the debugger stops in an internal function.
+    Handle<SharedFunctionInfo> shared_info(function_->shared());
+    Handle<ScopeInfo> scope_info(shared_info->scope_info());
+    if (shared_info->script() == isolate->heap()->undefined_value()) {
+      while (context_->closure() == *function_) {
+        context_ = Handle<Context>(context_->previous(), isolate_);
+      }
+      return;
+    }
+
+    // Get the debug info (create it if it does not exist).
+    if (!isolate->debug()->EnsureDebugInfo(shared_info)) {
+      // Return if ensuring debug info failed.
+      return;
+    }
+    Handle<DebugInfo> debug_info = Debug::GetDebugInfo(shared_info);
+
+    // Find the break point where execution has stopped.
+    BreakLocationIterator break_location_iterator(debug_info,
+                                                  ALL_BREAK_LOCATIONS);
+    break_location_iterator.FindBreakLocationFromAddress(frame->pc());
+    if (break_location_iterator.IsExit()) {
+      // We are within the return sequence. At the momemt it is not possible to
+      // get a source position which is consistent with the current scope chain.
+      // Thus all nested with, catch and block contexts are skipped and we only
+      // provide the function scope.
+      if (scope_info->HasContext()) {
+        context_ = Handle<Context>(context_->declaration_context(), isolate_);
+      } else {
+        while (context_->closure() == *function_) {
+          context_ = Handle<Context>(context_->previous(), isolate_);
+        }
+      }
+      if (scope_info->Type() != EVAL_SCOPE) nested_scope_chain_.Add(scope_info);
+    } else {
+      // Reparse the code and analyze the scopes.
+      ZoneScope zone_scope(isolate, DELETE_ON_EXIT);
+      Handle<Script> script(Script::cast(shared_info->script()));
+      Scope* scope = NULL;
+
+      // Check whether we are in global, eval or function code.
+      Handle<ScopeInfo> scope_info(shared_info->scope_info());
+      if (scope_info->Type() != FUNCTION_SCOPE) {
+        // Global or eval code.
+        CompilationInfo info(script);
+        if (scope_info->Type() == GLOBAL_SCOPE) {
+          info.MarkAsGlobal();
+        } else {
+          ASSERT(scope_info->Type() == EVAL_SCOPE);
+          info.MarkAsEval();
+          info.SetCallingContext(Handle<Context>(function_->context()));
+        }
+        if (ParserApi::Parse(&info, kNoParsingFlags) && Scope::Analyze(&info)) {
+          scope = info.function()->scope();
+        }
+      } else {
+        // Function code
+        CompilationInfo info(shared_info);
+        if (ParserApi::Parse(&info, kNoParsingFlags) && Scope::Analyze(&info)) {
+          scope = info.function()->scope();
+        }
+      }
+
+      // Retrieve the scope chain for the current position.
+      if (scope != NULL) {
+        int source_position = shared_info->code()->SourcePosition(frame_->pc());
+        scope->GetNestedScopeChain(&nested_scope_chain_, source_position);
+      } else {
+        // A failed reparse indicates that the preparser has diverged from the
+        // parser or that the preparse data given to the initial parse has been
+        // faulty. We fail in debug mode but in release mode we only provide the
+        // information we get from the context chain but nothing about
+        // completely stack allocated scopes or stack allocated locals.
+        UNREACHABLE();
+      }
     }
   }
 
@@ -11230,40 +11286,49 @@ class ScopeIterator {
 
   // Move to the next scope.
   void Next() {
-    // If at a local scope mark the local scope as passed.
-    if (at_local_) {
-      at_local_ = false;
-      local_done_ = true;
-
-      // If the current context is not associated with the local scope the
-      // current context is the next real scope, so don't move to the next
-      // context in this case.
-      if (context_->closure() != *function_) {
-        return;
-      }
-    }
-
-    // The global scope is always the last in the chain.
-    if (context_->IsGlobalContext()) {
+    ScopeType scope_type = Type();
+    if (scope_type == ScopeTypeGlobal) {
+      // The global scope is always the last in the chain.
+      ASSERT(context_->IsGlobalContext());
       context_ = Handle<Context>();
       return;
     }
-
-    // Move to the next context.
-    context_ = Handle<Context>(context_->previous(), isolate_);
-
-    // If passing the local scope indicate that the current scope is now the
-    // local scope.
-    if (!local_done_ &&
-        (context_->IsGlobalContext() || context_->IsFunctionContext())) {
-      at_local_ = true;
+    if (nested_scope_chain_.is_empty()) {
+      context_ = Handle<Context>(context_->previous(), isolate_);
+    } else {
+      if (nested_scope_chain_.last()->HasContext()) {
+        ASSERT(context_->previous() != NULL);
+        context_ = Handle<Context>(context_->previous(), isolate_);
+      }
+      nested_scope_chain_.RemoveLast();
     }
   }
 
   // Return the type of the current scope.
   ScopeType Type() {
-    if (at_local_) {
-      return ScopeTypeLocal;
+    if (!nested_scope_chain_.is_empty()) {
+      Handle<ScopeInfo> scope_info = nested_scope_chain_.last();
+      switch (scope_info->Type()) {
+        case FUNCTION_SCOPE:
+          ASSERT(context_->IsFunctionContext() ||
+                 !scope_info->HasContext());
+          return ScopeTypeLocal;
+        case GLOBAL_SCOPE:
+          ASSERT(context_->IsGlobalContext());
+          return ScopeTypeGlobal;
+        case WITH_SCOPE:
+          ASSERT(context_->IsWithContext());
+          return ScopeTypeWith;
+        case CATCH_SCOPE:
+          ASSERT(context_->IsCatchContext());
+          return ScopeTypeCatch;
+        case BLOCK_SCOPE:
+          ASSERT(!scope_info->HasContext() ||
+                 context_->IsBlockContext());
+          return ScopeTypeBlock;
+        case EVAL_SCOPE:
+          UNREACHABLE();
+      }
     }
     if (context_->IsGlobalContext()) {
       ASSERT(context_->global()->IsGlobalObject());
@@ -11289,6 +11354,7 @@ class ScopeIterator {
         return Handle<JSObject>(CurrentContext()->global());
       case ScopeIterator::ScopeTypeLocal:
         // Materialize the content of the local scope into a JSObject.
+        ASSERT(nested_scope_chain_.length() == 1);
         return MaterializeLocalScope(isolate_, frame_, inlined_frame_index_);
       case ScopeIterator::ScopeTypeWith:
         // Return the with object.
@@ -11305,13 +11371,28 @@ class ScopeIterator {
     return Handle<JSObject>();
   }
 
+  Handle<ScopeInfo> CurrentScopeInfo() {
+    if (!nested_scope_chain_.is_empty()) {
+      return nested_scope_chain_.last();
+    } else if (context_->IsBlockContext()) {
+      return Handle<ScopeInfo>(ScopeInfo::cast(context_->extension()));
+    } else if (context_->IsFunctionContext()) {
+      return Handle<ScopeInfo>(context_->closure()->shared()->scope_info());
+    }
+    return Handle<ScopeInfo>::null();
+  }
+
   // Return the context for this scope. For the local context there might not
   // be an actual context.
   Handle<Context> CurrentContext() {
-    if (at_local_ && context_->closure() != *function_) {
+    if (Type() == ScopeTypeGlobal ||
+        nested_scope_chain_.is_empty()) {
+      return context_;
+    } else if (nested_scope_chain_.last()->HasContext()) {
+      return context_;
+    } else {
       return Handle<Context>();
     }
-    return context_;
   }
 
 #ifdef DEBUG
@@ -11373,8 +11454,7 @@ class ScopeIterator {
   int inlined_frame_index_;
   Handle<JSFunction> function_;
   Handle<Context> context_;
-  bool local_done_;
-  bool at_local_;
+  List<Handle<ScopeInfo> > nested_scope_chain_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ScopeIterator);
 };
@@ -11837,45 +11917,65 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_ClearStepping) {
 
 // Creates a copy of the with context chain. The copy of the context chain is
 // is linked to the function context supplied.
-static Handle<Context> CopyWithContextChain(Isolate* isolate,
-                                            Handle<JSFunction> function,
-                                            Handle<Context> current,
-                                            Handle<Context> base) {
-  // At the end of the chain. Return the base context to link to.
-  if (current->IsFunctionContext() || current->IsGlobalContext()) {
-    return base;
+static Handle<Context> CopyNestedScopeContextChain(Isolate* isolate,
+                                                   Handle<JSFunction> function,
+                                                   Handle<Context> base,
+                                                   JavaScriptFrame* frame,
+                                                   int inlined_frame_index) {
+  HandleScope scope(isolate);
+  List<Handle<ScopeInfo> > scope_chain;
+  List<Handle<Context> > context_chain;
+
+  ScopeIterator it(isolate, frame, inlined_frame_index);
+  for (; it.Type() != ScopeIterator::ScopeTypeGlobal &&
+         it.Type() != ScopeIterator::ScopeTypeLocal ; it.Next()) {
+    ASSERT(!it.Done());
+    scope_chain.Add(it.CurrentScopeInfo());
+    context_chain.Add(it.CurrentContext());
   }
 
-  // Recursively copy the with and catch contexts.
-  HandleScope scope(isolate);
-  Handle<Context> previous(current->previous());
-  Handle<Context> new_previous =
-      CopyWithContextChain(isolate, function, previous, base);
-  Handle<Context> new_current;
-  if (current->IsCatchContext()) {
-    Handle<String> name(String::cast(current->extension()));
-    Handle<Object> thrown_object(current->get(Context::THROWN_OBJECT_INDEX));
-    new_current =
-        isolate->factory()->NewCatchContext(function,
-                                            new_previous,
-                                            name,
-                                            thrown_object);
-  } else if (current->IsBlockContext()) {
-    Handle<ScopeInfo> scope_info(ScopeInfo::cast(current->extension()));
-    new_current =
-        isolate->factory()->NewBlockContext(function, new_previous, scope_info);
-    // Copy context slots.
-    int num_context_slots = scope_info->ContextLength();
-    for (int i = Context::MIN_CONTEXT_SLOTS; i < num_context_slots; ++i) {
-      new_current->set(i, current->get(i));
+  // At the end of the chain. Return the base context to link to.
+  Handle<Context> context = base;
+
+  // Iteratively copy and or materialize the nested contexts.
+  while (!scope_chain.is_empty()) {
+    Handle<ScopeInfo> scope_info = scope_chain.RemoveLast();
+    Handle<Context> current = context_chain.RemoveLast();
+    ASSERT(!(scope_info->HasContext() & current.is_null()));
+
+    if (scope_info->Type() == CATCH_SCOPE) {
+      Handle<String> name(String::cast(current->extension()));
+      Handle<Object> thrown_object(current->get(Context::THROWN_OBJECT_INDEX));
+      context =
+          isolate->factory()->NewCatchContext(function,
+                                              context,
+                                              name,
+                                              thrown_object);
+    } else if (scope_info->Type() == BLOCK_SCOPE) {
+      // Materialize the contents of the block scope into a JSObject.
+      Handle<JSObject> block_scope_object =
+          MaterializeBlockScope(isolate, current);
+      if (block_scope_object.is_null()) {
+        return Handle<Context>::null();
+      }
+      // Allocate a new function context for the debug evaluation and set the
+      // extension object.
+      Handle<Context> new_context =
+          isolate->factory()->NewFunctionContext(Context::MIN_CONTEXT_SLOTS,
+                                                 function);
+      new_context->set_extension(*block_scope_object);
+      new_context->set_previous(*context);
+      context = new_context;
+    } else {
+      ASSERT(scope_info->Type() == WITH_SCOPE);
+      ASSERT(current->IsWithContext());
+      Handle<JSObject> extension(JSObject::cast(current->extension()));
+      context =
+          isolate->factory()->NewWithContext(function, context, extension);
     }
-  } else {
-    ASSERT(current->IsWithContext());
-    Handle<JSObject> extension(JSObject::cast(current->extension()));
-    new_current =
-        isolate->factory()->NewWithContext(function, new_previous, extension);
   }
-  return scope.CloseAndEscape(new_current);
+
+  return scope.CloseAndEscape(context);
 }
 
 
@@ -12010,7 +12110,11 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_DebugEvaluate) {
   if (scope_info->HasContext()) {
     function_context = Handle<Context>(frame_context->declaration_context());
   }
-  context = CopyWithContextChain(isolate, go_between, frame_context, context);
+  context = CopyNestedScopeContextChain(isolate,
+                                        go_between,
+                                        context,
+                                        frame,
+                                        inlined_frame_index);
 
   if (additional_context->IsJSObject()) {
     Handle<JSObject> extension = Handle<JSObject>::cast(additional_context);