text: // Copyright 2013 the V8 project authors. All rights reserved.
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  //       notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  //       copyright notice, this list of conditions and the following
  //       disclaimer in the documentation and/or other materials provided
  //       with the distribution.
  //     * Neither the name of Google Inc. nor the names of its
  //       contributors may be used to endorse or promote products derived
  //       from this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  "use strict";
  
  // This file relies on the fact that the following declaration has been made
  // in runtime.js:
  // var $Array = global.Array;
  
  var $Symbol = global.Symbol;
  
  // -------------------------------------------------------------------
  
  function SymbolConstructor(x) {
    if (%_IsConstructCall()) {
      throw MakeTypeError('not_constructor', ["Symbol"]);
    }
    // NOTE: Passing in a Symbol value will throw on ToString().
    return %CreateSymbol(IS_UNDEFINED(x) ? x : ToString(x));
  }
  
  
  function SymbolToString() {
    if (!(IS_SYMBOL(this) || IS_SYMBOL_WRAPPER(this))) {
      throw MakeTypeError(
        'incompatible_method_receiver', ["Symbol.prototype.toString", this]);
    }
    var description = %SymbolDescription(%_ValueOf(this));
    return "Symbol(" + (IS_UNDEFINED(description) ? "" : description) + ")";
  }
  
  
  function SymbolValueOf() {
    if (!(IS_SYMBOL(this) || IS_SYMBOL_WRAPPER(this))) {
      throw MakeTypeError(
        'incompatible_method_receiver', ["Symbol.prototype.valueOf", this]);
    }
    return %_ValueOf(this);
  }
  
  
  function InternalSymbol(key) {
    var internal_registry = %SymbolRegistry().for_intern;
    if (IS_UNDEFINED(internal_registry[key])) {
      internal_registry[key] = %CreateSymbol(key);
    }
    return internal_registry[key];
  }
  
  
  function SymbolFor(key) {
    key = TO_STRING_INLINE(key);
    var registry = %SymbolRegistry();
    if (IS_UNDEFINED(registry.for[key])) {
      var symbol = %CreateSymbol(key);
      registry.for[key] = symbol;
      registry.keyFor[symbol] = key;
    }
    return registry.for[key];
  }
  
  
  function SymbolKeyFor(symbol) {
    if (!IS_SYMBOL(symbol)) throw MakeTypeError("not_a_symbol", [symbol]);
    return %SymbolRegistry().keyFor[symbol];
  }
  
  
  // ES6 19.1.2.8
  function ObjectGetOwnPropertySymbols(obj) {
    if (!IS_SPEC_OBJECT(obj)) {
      throw MakeTypeError("called_on_non_object",
                          ["Object.getOwnPropertySymbols"]);
    }
  
    // TODO(arv): Proxies use a shared trap for String and Symbol keys.
  
    return ObjectGetOwnPropertyKeys(obj, true);
  }
  
  
  //-------------------------------------------------------------------
  
  var symbolCreate = InternalSymbol("Symbol.create");
  var symbolHasInstance = InternalSymbol("Symbol.hasInstance");
  var symbolIsConcatSpreadable = InternalSymbol("Symbol.isConcatSpreadable");
  var symbolIsRegExp = InternalSymbol("Symbol.isRegExp");
  var symbolIterator = InternalSymbol("Symbol.iterator");
  var symbolToStringTag = InternalSymbol("Symbol.toStringTag");
  var symbolUnscopables = InternalSymbol("Symbol.unscopables");
  
  
  //-------------------------------------------------------------------
  
  function SetUpSymbol() {
    %CheckIsBootstrapping();
  
    %SetCode($Symbol, SymbolConstructor);
    %FunctionSetPrototype($Symbol, new $Object());
  
    InstallConstants($Symbol, $Array(
      "create", symbolCreate,
      "hasInstance", symbolHasInstance,
      "isConcatSpreadable", symbolIsConcatSpreadable,
      "isRegExp", symbolIsRegExp,
      "iterator", symbolIterator,
      "toStringTag", symbolToStringTag,
      "unscopables", symbolUnscopables
    ));
    InstallFunctions($Symbol, DONT_ENUM, $Array(
      "for", SymbolFor,
      "keyFor", SymbolKeyFor
    ));
  
    %SetProperty($Symbol.prototype, "constructor", $Symbol, DONT_ENUM);
    InstallFunctions($Symbol.prototype, DONT_ENUM, $Array(
      "toString", SymbolToString,
      "valueOf", SymbolValueOf
    ));
  }
  
  SetUpSymbol();
  
  
  function ExtendObject() {
    %CheckIsBootstrapping();
  
    InstallFunctions($Object, DONT_ENUM, $Array(
      "getOwnPropertySymbols", ObjectGetOwnPropertySymbols
    ));
  }
  
  ExtendObject();
  