[esnext] Implement Symbol.prototype.description

Proposal repo: https://github.com/tc39/proposal-symbol-description

Add new Builtin SymbolPrototypeDescriptionGetter.

Bug: v8:7807
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I7353bd00b172e91d8624e3373d2a4b55aced8b5c
Reviewed-on: https://chromium-review.googlesource.com/1088871
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53592}

src/bootstrapper.cc

@@ -4380,6 +4380,18 @@ void Genesis::InitializeGlobal_harmony_array_flat() {
                         Builtins::kArrayPrototypeFlatMap, 1, false, DONT_ENUM);
 }
 
+void Genesis::InitializeGlobal_harmony_symbol_description() {
+  if (!FLAG_harmony_symbol_description) return;
+
+  // Symbol.prototype.description
+  Handle<JSFunction> symbol_fun(native_context()->symbol_function());
+  Handle<JSObject> symbol_prototype(
+      JSObject::cast(symbol_fun->instance_prototype()));
+  SimpleInstallGetter(isolate(), symbol_prototype,
+                      factory()->InternalizeUtf8String("description"),
+                      Builtins::kSymbolPrototypeDescriptionGetter, true);
+}
+
 void Genesis::InitializeGlobal_harmony_string_matchall() {
   if (!FLAG_harmony_string_matchall) return;
 

src/builtins/builtins-definitions.h

@@ -1103,6 +1103,8 @@ namespace internal {
   CPP(SymbolFor)                                                               \
   /* ES6 #sec-symbol.keyfor */                                                 \
   CPP(SymbolKeyFor)                                                            \
+  /* ES #sec-symbol.prototype.description */                                   \
+  TFJ(SymbolPrototypeDescriptionGetter, 0)                                     \
   /* ES6 #sec-symbol.prototype-@@toprimitive */                                \
   TFJ(SymbolPrototypeToPrimitive, 1, kHint)                                    \
   /* ES6 #sec-symbol.prototype.tostring */                                     \

src/builtins/builtins-symbol-gen.cc

@@ -11,6 +11,16 @@ namespace internal {
 
 // -----------------------------------------------------------------------------
 // ES6 #sec-symbol-objects
+// ES ##sec-symbol.prototype.description
+TF_BUILTIN(SymbolPrototypeDescriptionGetter, CodeStubAssembler) {
+  Node* context = Parameter(Descriptor::kContext);
+  Node* receiver = Parameter(Descriptor::kReceiver);
+
+  Node* value = ToThisValue(context, receiver, PrimitiveType::kSymbol,
+                            "Symbol.prototype.description");
+  Node* result = LoadObjectField(value, Symbol::kNameOffset);
+  Return(result);
+}
 
 // ES6 #sec-symbol.prototype-@@toprimitive
 TF_BUILTIN(SymbolPrototypeToPrimitive, CodeStubAssembler) {

src/flag-definitions.h

@@ -208,10 +208,11 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_private_fields)
 // Update bootstrapper.cc whenever adding a new feature flag.
 
 // Features that are still work in progress (behind individual flags).
-#define HARMONY_INPROGRESS_BASE(V)                            \
-  V(harmony_do_expressions, "harmony do-expressions")         \
-  V(harmony_class_fields, "harmony fields in class literals") \
-  V(harmony_static_fields, "harmony static fields in class literals")
+#define HARMONY_INPROGRESS_BASE(V)                                    \
+  V(harmony_do_expressions, "harmony do-expressions")                 \
+  V(harmony_class_fields, "harmony fields in class literals")         \
+  V(harmony_static_fields, "harmony static fields in class literals") \
+  V(harmony_symbol_description, "harmony Symbol.prototype.description")
 
 #ifdef V8_INTL_SUPPORT
 #define HARMONY_INPROGRESS(V) \

test/mjsunit/harmony/symbol-description.js

+// Copyright 2018 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.
+
+// Flags: --harmony-symbol-description
+
+{
+  let desc = Object.getOwnPropertyDescriptor(Symbol.prototype, 'description');
+  assertEquals(desc.set, undefined);
+  assertEquals(desc.writable, undefined);
+  assertFalse(desc.enumerable);
+  assertTrue(desc.configurable);
+}
+
+{
+  const empty = Symbol();
+  assertEquals(empty.description, undefined);
+
+  const symbol = Symbol('test');
+  assertEquals(symbol.description, 'test');
+  assertFalse(symbol.hasOwnProperty('description'));
+}
+
+{
+  const empty = Object(Symbol());
+  assertEquals(empty.description, undefined);
+
+  const symbol = Object(Symbol('test'));
+  assertEquals(symbol.description, 'test');
+  assertFalse(symbol.hasOwnProperty('description'));
+}
+
+{
+  assertThrows(function() {
+    const proxy = new Proxy({}, {});
+    Symbol.prototype.description.call(proxy);
+  }, TypeError);
+
+  assertThrows(function() {
+    const smi = 123;
+    Symbol.prototype.description.call(smi);
+  }, TypeError);
+
+  assertThrows(function() {
+    const str = 'string';
+    Symbol.prototype.description.call(string);
+  }, TypeError);
+
+  assertThrows(function() {
+    const obj = { prop: 'test' };
+    Symbol.prototype.description.call(obj);
+  }, TypeError);
+}

tools/v8heapconst.py

@@ -266,33 +266,33 @@ KNOWN_MAPS = {
   ("RO_SPACE", 0x05019): (172, "Tuple2Map"),
   ("RO_SPACE", 0x05211): (170, "ScriptMap"),
   ("RO_SPACE", 0x053d9): (162, "InterceptorInfoMap"),
-  ("RO_SPACE", 0x09d21): (154, "AccessorInfoMap"),
-  ("RO_SPACE", 0x09f31): (153, "AccessCheckInfoMap"),
-  ("RO_SPACE", 0x09f99): (155, "AccessorPairMap"),
-  ("RO_SPACE", 0x0a001): (156, "AliasedArgumentsEntryMap"),
-  ("RO_SPACE", 0x0a069): (157, "AllocationMementoMap"),
-  ("RO_SPACE", 0x0a0d1): (158, "AllocationSiteMap"),
-  ("RO_SPACE", 0x0a139): (159, "AsyncGeneratorRequestMap"),
-  ("RO_SPACE", 0x0a1a1): (160, "DebugInfoMap"),
-  ("RO_SPACE", 0x0a209): (161, "FunctionTemplateInfoMap"),
-  ("RO_SPACE", 0x0a271): (163, "InterpreterDataMap"),
-  ("RO_SPACE", 0x0a2d9): (164, "ModuleInfoEntryMap"),
-  ("RO_SPACE", 0x0a341): (165, "ModuleMap"),
-  ("RO_SPACE", 0x0a3a9): (166, "ObjectTemplateInfoMap"),
-  ("RO_SPACE", 0x0a411): (167, "PromiseCapabilityMap"),
-  ("RO_SPACE", 0x0a479): (168, "PromiseReactionMap"),
-  ("RO_SPACE", 0x0a4e1): (169, "PrototypeInfoMap"),
-  ("RO_SPACE", 0x0a549): (171, "StackFrameInfoMap"),
-  ("RO_SPACE", 0x0a5b1): (173, "Tuple3Map"),
-  ("RO_SPACE", 0x0a619): (174, "WasmCompiledModuleMap"),
-  ("RO_SPACE", 0x0a681): (175, "WasmDebugInfoMap"),
-  ("RO_SPACE", 0x0a6e9): (176, "WasmExportedFunctionDataMap"),
-  ("RO_SPACE", 0x0a751): (177, "WasmSharedModuleDataMap"),
-  ("RO_SPACE", 0x0a7b9): (178, "CallableTaskMap"),
-  ("RO_SPACE", 0x0a821): (179, "CallbackTaskMap"),
-  ("RO_SPACE", 0x0a889): (180, "PromiseFulfillReactionJobTaskMap"),
-  ("RO_SPACE", 0x0a8f1): (181, "PromiseRejectReactionJobTaskMap"),
-  ("RO_SPACE", 0x0a959): (182, "PromiseResolveThenableJobTaskMap"),
+  ("RO_SPACE", 0x09d59): (154, "AccessorInfoMap"),
+  ("RO_SPACE", 0x09f69): (153, "AccessCheckInfoMap"),
+  ("RO_SPACE", 0x09fd1): (155, "AccessorPairMap"),
+  ("RO_SPACE", 0x0a039): (156, "AliasedArgumentsEntryMap"),
+  ("RO_SPACE", 0x0a0a1): (157, "AllocationMementoMap"),
+  ("RO_SPACE", 0x0a109): (158, "AllocationSiteMap"),
+  ("RO_SPACE", 0x0a171): (159, "AsyncGeneratorRequestMap"),
+  ("RO_SPACE", 0x0a1d9): (160, "DebugInfoMap"),
+  ("RO_SPACE", 0x0a241): (161, "FunctionTemplateInfoMap"),
+  ("RO_SPACE", 0x0a2a9): (163, "InterpreterDataMap"),
+  ("RO_SPACE", 0x0a311): (164, "ModuleInfoEntryMap"),
+  ("RO_SPACE", 0x0a379): (165, "ModuleMap"),
+  ("RO_SPACE", 0x0a3e1): (166, "ObjectTemplateInfoMap"),
+  ("RO_SPACE", 0x0a449): (167, "PromiseCapabilityMap"),
+  ("RO_SPACE", 0x0a4b1): (168, "PromiseReactionMap"),
+  ("RO_SPACE", 0x0a519): (169, "PrototypeInfoMap"),
+  ("RO_SPACE", 0x0a581): (171, "StackFrameInfoMap"),
+  ("RO_SPACE", 0x0a5e9): (173, "Tuple3Map"),
+  ("RO_SPACE", 0x0a651): (174, "WasmCompiledModuleMap"),
+  ("RO_SPACE", 0x0a6b9): (175, "WasmDebugInfoMap"),
+  ("RO_SPACE", 0x0a721): (176, "WasmExportedFunctionDataMap"),
+  ("RO_SPACE", 0x0a789): (177, "WasmSharedModuleDataMap"),
+  ("RO_SPACE", 0x0a7f1): (178, "CallableTaskMap"),
+  ("RO_SPACE", 0x0a859): (179, "CallbackTaskMap"),
+  ("RO_SPACE", 0x0a8c1): (180, "PromiseFulfillReactionJobTaskMap"),
+  ("RO_SPACE", 0x0a929): (181, "PromiseRejectReactionJobTaskMap"),
+  ("RO_SPACE", 0x0a991): (182, "PromiseResolveThenableJobTaskMap"),
   ("MAP_SPACE", 0x02201): (1057, "ExternalMap"),
   ("MAP_SPACE", 0x02259): (1072, "JSMessageObjectMap"),
 }