harmony_scoping: Implement lexical bindings at top level

src/runtime/runtime-scopes.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/frames-inl.h"
 #include "src/runtime/runtime-utils.h"
 #include "src/scopeinfo.h"
 #include "src/scopes.h"
 
 namespace v8 {
 namespace internal {
 
 static Object* ThrowRedeclarationError(Isolate* isolate, Handle<String> name) {
   HandleScope scope(isolate);
   Handle<Object> args[1] = {name};
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError("var_redeclaration", HandleVector(args, 1)));
 }
 
 
 // May throw a RedeclarationError.
 static Object* DeclareGlobals(Isolate* isolate, Handle<GlobalObject> global,
                               Handle<String> name, Handle<Object> value,
                               PropertyAttributes attr, bool is_var,
                               bool is_const, bool is_function) {
+  Handle<GlobalContextTable> global_contexts(
+      global->native_context()->global_context_table());
+  GlobalContextTable::LookupResult lookup;
+  if (GlobalContextTable::Lookup(global_contexts, name, &lookup) &&
+      IsLexicalVariableMode(lookup.mode)) {
+    return ThrowRedeclarationError(isolate, name);
+  }
+
   // Do the lookup own properties only, see ES5 erratum.
   LookupIterator it(global, name, LookupIterator::HIDDEN_SKIP_INTERCEPTOR);
   Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
   if (!maybe.has_value) return isolate->heap()->exception();
 
   if (it.IsFound()) {
     PropertyAttributes old_attributes = maybe.value;
     // The name was declared before; check for conflicting re-declarations.
     if (is_const) return ThrowRedeclarationError(isolate, name);
 
@@ skipping 460 matching lines @@
   CONVERT_ARG_HANDLE_CHECKED(SharedFunctionInfo, shared, 1);
   CONVERT_BOOLEAN_ARG_CHECKED(pretenure, 2);
 
   // The caller ensures that we pretenure closures that are assigned
   // directly to properties.
   PretenureFlag pretenure_flag = pretenure ? TENURED : NOT_TENURED;
   return *isolate->factory()->NewFunctionFromSharedFunctionInfo(shared, context,
                                                                 pretenure_flag);
 }
 
+static Object* FindNameClash(Handle<ScopeInfo> scope_info,

[adamk, 2014/11/06 20:18:06]

Not necessary in this patch, but this file could use some MaybeHandlification.

[Dmitry Lomov (no reviews), 2014/11/07 10:18:48]

Indeed. I'll prep a clean-up patch.

+                             Handle<GlobalObject> global_object,
+                             Handle<GlobalContextTable> global_context) {
+  Isolate* isolate = scope_info->GetIsolate();
+  for (int var = 0; var < scope_info->ContextLocalCount(); var++) {
+    Handle<String> name(scope_info->ContextLocalName(var));
+    VariableMode mode = scope_info->ContextLocalMode(var);
+    GlobalContextTable::LookupResult lookup;
+    if (GlobalContextTable::Lookup(global_context, name, &lookup)) {
+      if (IsLexicalVariableMode(mode) || IsLexicalVariableMode(lookup.mode)) {
+        return ThrowRedeclarationError(isolate, name);
+      }
+    }
+
+    if (IsLexicalVariableMode(mode)) {
+      LookupIterator it(global_object, name,
+                        LookupIterator::HIDDEN_SKIP_INTERCEPTOR);
+      Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
+      if (!maybe.has_value) return isolate->heap()->exception();

[adamk, 2014/11/06 20:18:06]

Why return exception here?

[Dmitry Lomov (no reviews), 2014/11/07 10:18:48]

Absence of value in Maybe<T> indicates exception, so we propagate that.
When GetPropertyAttributes cannot find a property, it returns maybe(ABSENT), so
the code below will execute even for absent properties, but it is no harm done.

+      if ((maybe.value & DONT_DELETE) != 0) {
+        return ThrowRedeclarationError(isolate, name);
+      }
+
+      GlobalObject::InvalidatePropertyCell(global_object, name);
+    }
+  }
+  return isolate->heap()->undefined_value();
+}
+
 
 RUNTIME_FUNCTION(Runtime_NewGlobalContext) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
 
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
   CONVERT_ARG_HANDLE_CHECKED(ScopeInfo, scope_info, 1);
+  Handle<GlobalObject> global_object(function->context()->global_object());
+  Handle<Context> native_context(global_object->native_context());
+  Handle<GlobalContextTable> global_context_table(
+      native_context->global_context_table());
+
+  Handle<String> clashed_name;
+  Object* name_clash_result =
+      FindNameClash(scope_info, global_object, global_context_table);
+  if (isolate->has_pending_exception()) return name_clash_result;
+
   Handle<Context> result =
       isolate->factory()->NewGlobalContext(function, scope_info);
 
   DCHECK(function->context() == isolate->context());
   DCHECK(function->context()->global_object() == result->global_object());
-  result->global_object()->set_global_context(*result);
+
+  Handle<GlobalContextTable> new_global_context_table =
+      GlobalContextTable::Extend(global_context_table, result);
+  native_context->set_global_context_table(*new_global_context_table);
   return *result;
 }
 
 
 RUNTIME_FUNCTION(Runtime_NewFunctionContext) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
 
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
 
@@ skipping 486 matching lines @@
   return Smi::FromInt(frame->GetArgumentsLength());
 }
 
 
 RUNTIME_FUNCTION(RuntimeReference_Arguments) {
   SealHandleScope shs(isolate);
   return __RT_impl_Runtime_GetArgumentsProperty(args, isolate);
 }
 }
 }  // namespace v8::internal