Filter out synthetic variables from with scopes

src/contexts.cc

Index: src/contexts.cc
diff --git a/src/contexts.cc b/src/contexts.cc
index 3447b42f47dc32d3f37055fc36d9fa30f365ab43..71fe7a9b381c726266aff2560e0e7868ecb3394b 100644
--- a/src/contexts.cc
+++ b/src/contexts.cc
@@ -227,6 +227,11 @@ Handle<Object> Context::Lookup(Handle<String> name, ContextLookupFlags flags,
          (context->IsWithContext() && ((flags & SKIP_WITH_CONTEXT) == 0)) ||
          context->IsFunctionContext() || context->IsBlockContext()) &&
         context->extension_receiver() != nullptr) {
+      // A dynamic context will never bind "this" or a synthetic variable;
+      // scope analysis has already ensured that these are resolved
+      // statically.
+      DCHECK(!ScopeInfo::VariableIsSynthetic(*name));
+
       Handle<JSReceiver> object(context->extension_receiver());
 
       if (context->IsNativeContext()) {
@@ -261,20 +266,15 @@ Handle<Object> Context::Lookup(Handle<String> name, ContextLookupFlags flags,
           object->IsJSContextExtensionObject()) {
         maybe = JSReceiver::GetOwnPropertyAttributes(object, name);
       } else if (context->IsWithContext()) {
-        // A with context will never bind "this".
-        if (name->Equals(*isolate->factory()->this_string())) {
-          maybe = Just(ABSENT);
+        LookupIterator it(object, name, object);
+        Maybe<bool> found = UnscopableLookup(&it);
+        if (found.IsNothing()) {
+          maybe = Nothing<PropertyAttributes>();
         } else {
-          LookupIterator it(object, name, object);
-          Maybe<bool> found = UnscopableLookup(&it);
-          if (found.IsNothing()) {
-            maybe = Nothing<PropertyAttributes>();
-          } else {
-            // Luckily, consumers of |maybe| only care whether the property
-            // was absent or not, so we can return a dummy |NONE| value
-            // for its attributes when it was present.
-            maybe = Just(found.FromJust() ? NONE : ABSENT);
-          }
+          // Luckily, consumers of |maybe| only care whether the property
+          // was absent or not, so we can return a dummy |NONE| value
+          // for its attributes when it was present.
+          maybe = Just(found.FromJust() ? NONE : ABSENT);
         }
       } else {
         maybe = JSReceiver::GetPropertyAttributes(object, name);