Add a --harmony-species flag, defining @@species on constructors

This patch adds the basis for subclassing TypedArrays, Arrays and
ArrayBuffers through the @@species hook, added in ES2015. This is
the first patch in a series. This patch simply defines the
@@species Symbol and installs it on the appropriate constructors.
The behavior is guarded behind the --harmony-species flag.

R=cbruni
BUG=v8:4093
LOG=Y
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1558543002

Cr-Commit-Position: refs/heads/master@{#33095}

BUILD.gn

@@ -286,6 +286,7 @@ action("js2c_experimental") {
     "src/js/harmony-object-observe.js",
     "src/js/harmony-sharedarraybuffer.js",
     "src/js/harmony-simd.js",
+    "src/js/harmony-species.js",
     "src/js/harmony-unicode-regexps.js",
     "src/js/promise-extra.js"
   ]

src/bootstrapper.cc

@@ -2145,6 +2145,7 @@ void Bootstrapper::ExportExperimentalFromRuntime(Isolate* isolate,
 
   INITIALIZE_FLAG(FLAG_harmony_tostring)
   INITIALIZE_FLAG(FLAG_harmony_tolength)
+  INITIALIZE_FLAG(FLAG_harmony_species)
 
 #undef INITIALIZE_FLAG
 }
@@ -2388,6 +2389,13 @@ Handle<JSFunction> Genesis::InstallArrayBuffer(Handle<JSObject> target,
 }
 
 
+void Genesis::InitializeGlobal_harmony_species() {
+  if (!FLAG_harmony_species) return;
+  InstallPublicSymbol(factory(), native_context(), "species",
+                      factory()->species_symbol());
+}
+
+
 Handle<JSFunction> Genesis::InstallInternalArray(Handle<JSObject> target,
                                                  const char* name,
                                                  ElementsKind elements_kind) {
@@ -2719,6 +2727,8 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_sloppy_natives[] = {nullptr};
   static const char* harmony_sloppy_function_natives[] = {nullptr};
   static const char* harmony_sloppy_let_natives[] = {nullptr};
+  static const char* harmony_species_natives[] = {"native harmony-species.js",
+                                                  nullptr};
   static const char* harmony_unicode_regexps_natives[] = {
       "native harmony-unicode-regexps.js", nullptr};
   static const char* harmony_default_parameters_natives[] = {nullptr};

src/flag-definitions.h

@@ -198,14 +198,15 @@ DEFINE_IMPLICATION(es_staging, harmony_regexp_lookbehind)
 DEFINE_IMPLICATION(es_staging, move_object_start)
 
 // Features that are still work in progress (behind individual flags).
-#define HARMONY_INPROGRESS(V)                                         \
-  V(harmony_modules, "harmony modules")                               \
-  V(harmony_unicode_regexps, "harmony unicode regexps")               \
-  V(harmony_function_name, "harmony Function name inference")         \
-  V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")           \
-  V(harmony_simd, "harmony simd")                                     \
-  V(harmony_do_expressions, "harmony do-expressions")                 \
-  V(harmony_regexp_subclass, "harmony regexp subclassing")
+#define HARMONY_INPROGRESS(V)                                 \
+  V(harmony_modules, "harmony modules")                       \
+  V(harmony_unicode_regexps, "harmony unicode regexps")       \
+  V(harmony_function_name, "harmony Function name inference") \
+  V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")   \
+  V(harmony_simd, "harmony simd")                             \
+  V(harmony_do_expressions, "harmony do-expressions")         \
+  V(harmony_regexp_subclass, "harmony regexp subclassing")    \
+  V(harmony_species, "harmony Symbol.species")
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                                 \

src/heap/heap.h

@@ -379,14 +379,15 @@ namespace internal {
   V(strong_function_transition_symbol)      \
   V(uninitialized_symbol)
 
-#define PUBLIC_SYMBOL_LIST(V)                 \
-  V(has_instance_symbol, Symbol.hasInstance)  \
-  V(iterator_symbol, Symbol.iterator)         \
-  V(match_symbol, Symbol.match)               \
-  V(replace_symbol, Symbol.replace)           \
-  V(search_symbol, Symbol.search)             \
-  V(split_symbol, Symbol.split)               \
-  V(to_primitive_symbol, Symbol.toPrimitive)  \
+#define PUBLIC_SYMBOL_LIST(V)                \
+  V(has_instance_symbol, Symbol.hasInstance) \
+  V(iterator_symbol, Symbol.iterator)        \
+  V(match_symbol, Symbol.match)              \
+  V(replace_symbol, Symbol.replace)          \
+  V(search_symbol, Symbol.search)            \
+  V(species_symbol, Symbol.species)          \
+  V(split_symbol, Symbol.split)              \
+  V(to_primitive_symbol, Symbol.toPrimitive) \
   V(unscopables_symbol, Symbol.unscopables)
 
 // Well-Known Symbols are "Public" symbols, which have a bit set which causes

src/js/harmony-species.js

+// Copyright 2015 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.
+
+(function(global, utils, extrasUtils) {
+
+"use strict";
+
+%CheckIsBootstrapping();
+
+var GlobalArray = global.Array;
+// It is important that this file is run after src/js/typedarray.js,
+// otherwise GlobalTypedArray would be Object, and we would break
+// old versions of Zepto.
+var GlobalTypedArray = global.Uint8Array.__proto__;
+var GlobalMap = global.Map;
+var GlobalSet = global.Set;
+var GlobalArrayBuffer = global.ArrayBuffer;
+var GlobalPromise = global.Promise;
+var GlobalRegExp = global.RegExp;
+var speciesSymbol = utils.ImportNow("species_symbol");
+
+function ArraySpecies() {
+  return this;
+}
+
+function TypedArraySpecies() {
+  return this;
+}
+
+function MapSpecies() {
+  return this;
+}
+
+function SetSpecies() {
+  return this;
+}
+
+function ArrayBufferSpecies() {
+  return this;
+}
+
+function PromiseSpecies() {
+  return this;
+}
+
+function RegExpSpecies() {
+  return this;
+}
+
+utils.InstallGetter(GlobalArray, speciesSymbol, ArraySpecies, DONT_ENUM);
+utils.InstallGetter(GlobalTypedArray, speciesSymbol, TypedArraySpecies, DONT_ENUM);
+utils.InstallGetter(GlobalMap, speciesSymbol, MapSpecies, DONT_ENUM);
+utils.InstallGetter(GlobalSet, speciesSymbol, SetSpecies, DONT_ENUM);
+utils.InstallGetter(GlobalArrayBuffer, speciesSymbol, ArrayBufferSpecies,
+                    DONT_ENUM);
+utils.InstallGetter(GlobalPromise, speciesSymbol, PromiseSpecies, DONT_ENUM);
+utils.InstallGetter(GlobalRegExp, speciesSymbol, RegExpSpecies, DONT_ENUM);
+
+});

src/js/prologue.js

@@ -221,6 +221,7 @@ function PostNatives(utils) {
     "regexp_flags_symbol",
     "to_string_tag_symbol",
     "object_to_string",
+    "species_symbol",
   ];
 
   var filtered_exports = {};

test/mjsunit/harmony/species.js

+// Copyright 2015 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-species
+
+// Test the ES2015 @@species feature
+
+'use strict';
+
+let TypedArray = Uint8Array.__proto__;
+
+// The @@species property exists on the right objects and has the right values
+
+let classesWithSpecies = [RegExp, Array, TypedArray, ArrayBuffer, Map, Set, Promise];
+let classesWithoutSpecies = [Object, Function, String, Number, Symbol, WeakMap, WeakSet];
+
+for (let constructor of classesWithSpecies) {
+  assertEquals(constructor, constructor[Symbol.species]);
+  assertThrows(function() { constructor[Symbol.species] = undefined }, TypeError);
+  let descriptor = Object.getOwnPropertyDescriptor(constructor, Symbol.species);
+  assertTrue(descriptor.configurable);
+  assertFalse(descriptor.enumerable);
+  assertEquals(undefined, descriptor.writable);
+  assertEquals(undefined, descriptor.set);
+  assertEquals('function', typeof descriptor.get);
+}
+
+// @@species is defined with distinct getters
+assertEquals(classesWithSpecies.length,
+             new Set(classesWithSpecies.map(constructor =>
+                                            Object.getOwnPropertyDescriptor(
+                                              constructor, Symbol.species).get)
+                ).size);
+
+for (let constructor of classesWithoutSpecies)
+  assertEquals(undefined, constructor[Symbol.species]);

tools/gyp/v8.gyp

@@ -1927,6 +1927,7 @@
           '../../src/js/harmony-object-observe.js',
           '../../src/js/harmony-sharedarraybuffer.js',
           '../../src/js/harmony-simd.js',
+          '../../src/js/harmony-species.js',
           '../../src/js/harmony-unicode-regexps.js',
           '../../src/js/promise-extra.js',
         ],