Confusion on changing data property callback attributes

src/objects.h

 // Copyright 2012 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include "allocation.h"
 #include "assert-scope.h"
 #include "builtins.h"
@@ skipping 2136 matching lines @@
 
   MUST_USE_RESULT static MaybeHandle<Object> SetPropertyForResult(
       Handle<JSObject> object,
       LookupResult* result,
       Handle<Name> name,
       Handle<Object> value,
       PropertyAttributes attributes,
       StrictMode strict_mode,
       StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
 
+  // SetLocalPropertyIgnoreAttributes converts callbacks to fields. We need to
+  // grant an exemption to ExecutableAccessor callbacks in some cases.
+  enum ExecutableAccessorInfoHandling {
+    DEFAULT_HANDLING,
+    DONT_FORCE_FIELD
+  };
+
   MUST_USE_RESULT static MaybeHandle<Object> SetOwnPropertyIgnoreAttributes(
       Handle<JSObject> object,
       Handle<Name> key,
       Handle<Object> value,
       PropertyAttributes attributes,
       ValueType value_type = OPTIMAL_REPRESENTATION,
       StoreMode mode = ALLOW_AS_CONSTANT,
       ExtensibilityCheck extensibility_check = PERFORM_EXTENSIBILITY_CHECK,
-      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
+      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED,
+      ExecutableAccessorInfoHandling handling = DEFAULT_HANDLING);
 
   static inline Handle<String> ExpectedTransitionKey(Handle<Map> map);
   static inline Handle<Map> ExpectedTransitionTarget(Handle<Map> map);
 
   // Try to follow an existing transition to a field with attributes NONE. The
   // return value indicates whether the transition was successful.
   static inline Handle<Map> FindTransitionToField(Handle<Map> map,
                                                   Handle<Name> key);
 
   // Extend the receiver with a single fast property appeared first in the
@@ skipping 8353 matching lines @@
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExecutableAccessorInfo)
   DECLARE_VERIFIER(ExecutableAccessorInfo)
 
   static const int kGetterOffset = AccessorInfo::kSize;
   static const int kSetterOffset = kGetterOffset + kPointerSize;
   static const int kDataOffset = kSetterOffset + kPointerSize;
   static const int kSize = kDataOffset + kPointerSize;
 
+  inline void clear_setter();
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExecutableAccessorInfo);
 };
 
 
 // Support for JavaScript accessors: A pair of a getter and a setter. Each
 // accessor can either be
 //   * a pointer to a JavaScript function or proxy: a real accessor
 //   * undefined: considered an accessor by the spec, too, strangely enough
 //   * the hole: an accessor which has not been set
@@ skipping 515 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_