Filter out synthetic variables from with scopes

src/contexts.cc

 // Copyright 2011 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/contexts.h"
 
 #include "src/bootstrapper.h"
 #include "src/debug/debug.h"
 #include "src/isolate-inl.h"
 
@@ skipping 243 matching lines @@
       }
 
       // 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.
       Maybe<PropertyAttributes> maybe = Nothing<PropertyAttributes>();
       if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
           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())) {
+        // A with context will never bind "this", but debug-eval may look into
+        // a with context when resolving "this". Other synthetic variables such
+        // as new.target may be resolved as DYNAMIC_LOCAL due to bug v8:5405 ,
+        // skipping them here serves as a workaround until a more thorough
+        // fix can be applied.
+        // TODO(v8:5405): Replace this check with a DCHECK when resolution of
+        // of synthetic variables does not go through this code path.
+        if (ScopeInfo::VariableIsSynthetic(*name)) {
           maybe = Just(ABSENT);
         } 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.
@@ skipping 306 matching lines @@
 
   int previous_value = errors_thrown()->value();
   set_errors_thrown(Smi::FromInt(previous_value + 1));
 }
 
 
 int Context::GetErrorsThrown() { return errors_thrown()->value(); }
 
 }  // namespace internal
 }  // namespace v8