Install "name" property on anonymous classes

This is a normative PR that reached consensus at the June 2019 TC39:
https://github.com/tc39/test262/pull/2299

Bug: v8:9646
Change-Id: I8cb927b9e9231dfb71ebf47171205a096350e38b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2360905
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69460}

src/objects/literal-objects-inl.h

@@ -95,14 +95,8 @@ void ObjectBoilerplateDescription::set_backing_store_size(
 OBJECT_CONSTRUCTORS_IMPL(ClassBoilerplate, FixedArray)
 CAST_ACCESSOR(ClassBoilerplate)
 
-BIT_FIELD_ACCESSORS(ClassBoilerplate, flags, install_class_name_accessor,
-                    ClassBoilerplate::Flags::InstallClassNameAccessorBit)
-
-BIT_FIELD_ACCESSORS(ClassBoilerplate, flags, arguments_count,
-                    ClassBoilerplate::Flags::ArgumentsCountBits)
-
-SMI_ACCESSORS(ClassBoilerplate, flags,
-              FixedArray::OffsetOfElementAt(kFlagsIndex))
+SMI_ACCESSORS(ClassBoilerplate, arguments_count,
+              FixedArray::OffsetOfElementAt(kArgumentsCountIndex))
 
 ACCESSORS(ClassBoilerplate, static_properties_template, Object,
           FixedArray::OffsetOfElementAt(kClassPropertiesTemplateIndex))

src/objects/literal-objects.cc

@@ -551,32 +551,24 @@ Handle<ClassBoilerplate> ClassBoilerplate::BuildClassBoilerplate(
     }
   }
 
-  // Add name accessor to the class object if necessary.
-  bool install_class_name_accessor = false;
+  // All classes, even anonymous ones, have a name accessor. If static_desc is
+  // in dictionary mode, the name accessor is installed at runtime in
+  // DefineClass.
   if (!expr->has_name_static_property() &&
-      expr->constructor()->has_shared_name()) {
-    if (static_desc.HasDictionaryProperties()) {
-      // Install class name accessor if necessary during class literal
-      // instantiation.
-      install_class_name_accessor = true;
-    } else {
-      // Set class name accessor if the "name" method was not added yet.
-      PropertyAttributes attribs =
-          static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);
-      static_desc.AddConstant(isolate, factory->name_string(),
-                              factory->function_name_accessor(), attribs);
-    }
+      !static_desc.HasDictionaryProperties()) {
+    // Set class name accessor if the "name" method was not added yet.
+    PropertyAttributes attribs =
+        static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);
+    static_desc.AddConstant(isolate, factory->name_string(),
+                            factory->function_name_accessor(), attribs);
   }
 
   static_desc.Finalize(isolate);
   instance_desc.Finalize(isolate);
 
   Handle<ClassBoilerplate> class_boilerplate = Handle<ClassBoilerplate>::cast(
-      factory->NewFixedArray(kBoileplateLength, AllocationType::kOld));
+      factory->NewFixedArray(kBoilerplateLength, AllocationType::kOld));
 
-  class_boilerplate->set_flags(0);
-  class_boilerplate->set_install_class_name_accessor(
-      install_class_name_accessor);
   class_boilerplate->set_arguments_count(dynamic_argument_index);
 
   class_boilerplate->set_static_properties_template(

src/objects/literal-objects.h

@@ -77,14 +77,6 @@ class ClassBoilerplate : public FixedArray {
  public:
   enum ValueKind { kData, kGetter, kSetter };
 
-  struct Flags {
-#define FLAGS_BIT_FIELDS(V, _)               \
-  V(InstallClassNameAccessorBit, bool, 1, _) \
-  V(ArgumentsCountBits, int, 30, _)
-    DEFINE_BIT_FIELDS(FLAGS_BIT_FIELDS)
-#undef FLAGS_BIT_FIELDS
-  };
-
   struct ComputedEntryFlags {
 #define COMPUTED_ENTRY_BIT_FIELDS(V, _) \
   V(ValueKindBits, ValueKind, 2, _)     \
@@ -133,14 +125,14 @@ class ClassBoilerplate : public FixedArray {
                                                         ClassLiteral* expr);
 
   enum {
-    kFlagsIndex,
+    kArgumentsCountIndex,
     kClassPropertiesTemplateIndex,
     kClassElementsTemplateIndex,
     kClassComputedPropertiesIndex,
     kPrototypePropertiesTemplateIndex,
     kPrototypeElementsTemplateIndex,
     kPrototypeComputedPropertiesIndex,
-    kBoileplateLength  // last element
+    kBoilerplateLength  // last element
   };
 
  private:

src/runtime/runtime-classes.cc

@@ -537,7 +537,7 @@ bool InitClassPrototype(Isolate* isolate,
     map->set_may_have_interesting_symbols(true);
     map->set_construction_counter(Map::kNoSlackTracking);
 
-    // We care about name property only for class constructor.
+    // Class prototypes do not have a name accessor.
     const bool install_name_accessor = false;
 
     return AddDescriptorsByTemplate(
@@ -592,8 +592,8 @@ bool InitClassConstructor(
     map->set_may_have_interesting_symbols(true);
     map->set_construction_counter(Map::kNoSlackTracking);
 
-    bool install_name_accessor =
-        class_boilerplate->install_class_name_accessor() != 0;
+    // All class constructors have a name accessor.
+    const bool install_name_accessor = true;
 
     return AddDescriptorsByTemplate(
         isolate, map, properties_dictionary_template,

test/mjsunit/es6/classes.js

@@ -36,8 +36,11 @@
 
   literal = { __proto__: class {} };
   assertEquals('', literal.__proto__.name);
-  assertEquals(
-      undefined, Object.getOwnPropertyDescriptor(literal.__proto__, 'name'));
+  var nameDescr = Object.getOwnPropertyDescriptor(literal.__proto__, 'name');
+  assertEquals('', nameDescr.value);
+  assertFalse(nameDescr.writable);
+  assertFalse(nameDescr.enumerable);
+  assertTrue(nameDescr.configurable);
 
   literal = { __proto__: class F {} };
   assertEquals('F', literal.__proto__.name);

test/mjsunit/es6/function-name.js

@@ -394,7 +394,7 @@
 })();
 
 (function testClassNameOrder() {
-  assertEquals(['length', 'prototype'], Object.getOwnPropertyNames(class {}));
+  assertEquals(['length', 'prototype', 'name'], Object.getOwnPropertyNames(class {}));
 
   var tmp = {'': class {}};
   var Tmp = tmp[''];

test/mjsunit/regress/regress-7773.js

@@ -44,7 +44,8 @@
   };
 
   // Anonymous classes do not have a "name" property by default.
-  assertSame(undefined, Object.getOwnPropertyDescriptor(class {}, 'name'));
+  descriptor.value = '';
+  assertEquals(descriptor, Object.getOwnPropertyDescriptor(class {}, 'name'));
   descriptor.value = 'C';
   assertEquals(descriptor, Object.getOwnPropertyDescriptor(class C {}, 'name'));
 
@@ -55,8 +56,9 @@
 
   let b = { __proto__: class {} };
   assertSame('', b.__proto__.name);
-  assertSame(
-      undefined, Object.getOwnPropertyDescriptor(b.__proto__, 'name'));
+  descriptor.value = '';
+  assertEquals(
+    descriptor, Object.getOwnPropertyDescriptor(b.__proto__, 'name'));
 
   let c = { fn: class F {} };
   assertSame('F', c.fn.name);

test/test262/test262.status

@@ -504,7 +504,6 @@
 
   # https://bugs.chromium.org/p/v8/issues/detail?id=9646
   'built-ins/ThrowTypeError/name': [FAIL],
-  'language/expressions/class/name': [FAIL],
 
   # https://bugs.chromium.org/p/v8/issues/detail?id=9742
   'intl402/Locale/getters': [FAIL],