Revert "Merge arguments branch to bleeding merge."

src/contexts.cc

Index: src/contexts.cc
diff --git a/src/contexts.cc b/src/contexts.cc
index 78e6f0c2966a0aa32a8be63b7ede4d5fc440c04a..2ed53788c026a538dd29714b8bfa9bd588b6b761 100644
--- a/src/contexts.cc
+++ b/src/contexts.cc
@@ -74,10 +74,8 @@ void Context::set_global_proxy(JSObject* object) {
 }
 
 
-Handle<Object> Context::Lookup(Handle<String> name,
-                               ContextLookupFlags flags,
-                               int* index_,
-                               PropertyAttributes* attributes) {
+Handle<Object> Context::Lookup(Handle<String> name, ContextLookupFlags flags,
+                               int* index_, PropertyAttributes* attributes) {
   Isolate* isolate = GetIsolate();
   Handle<Context> context(this, isolate);
 
@@ -100,35 +98,53 @@ Handle<Object> Context::Lookup(Handle<String> name,
 
     // Check extension/with/global object.
     if (context->has_extension()) {
-      Handle<JSObject> extension = Handle<JSObject>(context->extension(),
-                                                    isolate);
-      // Context extension objects needs to behave as if they have no
-      // prototype.  So even if we want to follow prototype chains, we
-      // need to only do a local lookup for context extension objects.
-      if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
-          extension->IsJSContextExtensionObject()) {
-        *attributes = extension->GetLocalPropertyAttribute(*name);
+      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;
+          return context;
+        }
       } else {
-        *attributes = extension->GetPropertyAttribute(*name);
-      }
-      if (*attributes != ABSENT) {
-        if (FLAG_trace_contexts) {
-          PrintF("=> found property in context object %p\n",
-                 reinterpret_cast<void*>(*extension));
+        // Global, function, and with contexts may have an object in the
+        // extension slot.
+        Handle<JSObject> extension(JSObject::cast(context->extension()),
+                                   isolate);
+        // Context extension objects needs to behave as if they have no
+        // prototype.  So even if we want to follow prototype chains, we
+        // need to only do a local lookup for context extension objects.
+        if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
+            extension->IsJSContextExtensionObject()) {
+          *attributes = extension->GetLocalPropertyAttribute(*name);
+        } else {
+          *attributes = extension->GetPropertyAttribute(*name);
+        }
+        if (*attributes != ABSENT) {
+          // property found
+          if (FLAG_trace_contexts) {
+            PrintF("=> found property in context object %p\n",
+                   reinterpret_cast<void*>(*extension));
+          }
+          return extension;
         }
-        return extension;
       }
     }
 
     // Only functions can have locals, parameters, and a function name.
     if (context->IsFunctionContext()) {
-      // We may have context-local slots.  Check locals in the context.
+      // we have context-local slots
+
+      // check non-parameter locals in context
       Handle<SerializedScopeInfo> scope_info(
           context->closure()->shared()->scope_info(), isolate);
       Variable::Mode mode;
       int index = scope_info->ContextSlotIndex(*name, &mode);
       ASSERT(index < 0 || index >= MIN_CONTEXT_SLOTS);
       if (index >= 0) {
+        // slot found
         if (FLAG_trace_contexts) {
           PrintF("=> found local in context slot %d (mode = %d)\n",
                  index, mode);
@@ -141,28 +157,39 @@ Handle<Object> Context::Lookup(Handle<String> name,
         // declared variables that were introduced through declaration nodes)
         // must not appear here.
         switch (mode) {
-          case Variable::INTERNAL:  // Fall through.
-          case Variable::VAR:
-            *attributes = NONE;
-            break;
-          case Variable::CONST:
-            *attributes = READ_ONLY;
-            break;
-          case Variable::DYNAMIC:
-          case Variable::DYNAMIC_GLOBAL:
-          case Variable::DYNAMIC_LOCAL:
-          case Variable::TEMPORARY:
-            UNREACHABLE();
-            break;
+          case Variable::INTERNAL:  // fall through
+          case Variable::VAR: *attributes = NONE; break;
+          case Variable::CONST: *attributes = READ_ONLY; break;
+          case Variable::DYNAMIC: UNREACHABLE(); break;
+          case Variable::DYNAMIC_GLOBAL: UNREACHABLE(); break;
+          case Variable::DYNAMIC_LOCAL: UNREACHABLE(); break;
+          case Variable::TEMPORARY: UNREACHABLE(); break;
         }
         return context;
       }
 
-      // Check the slot corresponding to the intermediate context holding
-      // only the function name variable.
+      // check parameter locals in context
+      int param_index = scope_info->ParameterIndex(*name);
+      if (param_index >= 0) {
+        // slot found.
+        int index = scope_info->ContextSlotIndex(
+            isolate->heap()->arguments_shadow_symbol(), NULL);
+        ASSERT(index >= 0);  // arguments must exist and be in the heap context
+        Handle<JSObject> arguments(JSObject::cast(context->get(index)),
+                                   isolate);
+        if (FLAG_trace_contexts) {
+          PrintF("=> found parameter %d in arguments object\n", param_index);
+        }
+        *index_ = param_index;
+        *attributes = NONE;
+        return arguments;
+      }
+
+      // check intermediate context (holding only the function name variable)
       if (follow_context_chain) {
         int index = scope_info->FunctionContextSlotIndex(*name);
         if (index >= 0) {
+          // slot found
           if (FLAG_trace_contexts) {
             PrintF("=> found intermediate function in context slot %d\n",
                    index);
@@ -182,6 +209,7 @@ Handle<Object> Context::Lookup(Handle<String> name,
     }
   } while (follow_context_chain);
 
+  // slot not found
   if (FLAG_trace_contexts) {
     PrintF("=> no property/slot found\n");
   }
@@ -196,8 +224,8 @@ bool Context::GlobalIfNotShadowedByEval(Handle<String> name) {
   // before the global context and check that there are no context
   // extension objects (conservative check for with statements).
   while (!context->IsGlobalContext()) {
-    // Check if the context is a catch or with context, or has called
-    // non-strict eval.
+    // Check if the context is a catch or with context, or has introduced
+    // bindings by calling non-strict eval.
     if (context->has_extension()) return false;
 
     // Not a with context so it must be a function context.