Implement the Symbol builtin object (#2601)

This patch contains the base functionalities that the new builtin object requires.

Currently unavailable:
 - print (Symbol('foo')) - this features requires the refactor of the print handler function
 - Several global symbol based builtin routines (follow up patch)

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

tests/jerry/es2015/symbol.js

@@ -0,0 +1,122 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+var a = Symbol ('foo');
+var b = Symbol ('bar');
+
+assert (a !== b);
+assert (a === a);
+assert (typeof a === 'symbol');
+assert (a.toString() == 'Symbol(foo)');
+assert (Object.prototype.toString.call (a) === "[object Symbol]");
+assert (JSON.stringify (a) === undefined);
+
+var obj = { c : 10, d : 20};
+obj[a] = 'EnumerableSymbolProp';
+assert (obj[a] === 'EnumerableSymbolProp');
+
+// Symbol properties are not listed via for in
+Object.defineProperty(obj, b, { value : 'NonEnumerableSymbolProp' });
+
+var counter = 0;
+
+for (var v in obj) {
+  assert (v === 'c' || v === 'd');
+  counter++;
+}
+
+assert (counter === 2);
+
+var keys = Object.keys (obj);
+assert (keys.length === 2);
+assert (keys[0] === 'c' || keys[0] === 'd');
+assert (keys[1] === 'd' || keys[1] === 'c');
+
+var c = Symbol ('bar');
+var obj2 = {};
+obj2[b] = 'foo';
+obj2[c] = 'bar';
+
+assert (obj2[b] == 'foo');
+assert (obj2[c] == 'bar');
+
+try {
+  new Date (Symbol ('2018-11-09'));
+  assert (false);
+} catch (e) {
+  assert (e instanceof TypeError);
+}
+
+try {
+  a + 'append_string';
+  assert (false);
+} catch (e) {
+  assert (e instanceof TypeError);
+}
+
+assert (Object (a) == a);
+assert (Object (a) !== a);
+
+// Test built-in symbols
+var a = ['hasInstance',
+         'isConcatSpreadable',
+         'iterator',
+         'match',
+         'replace',
+         'search',
+         'species',
+         'split',
+         'toPrimitive',
+         'toStringTag',
+         'unscopables'];
+
+a.forEach (function (e) {
+  assert (Symbol[e].toString() === ('Symbol(Symbol.' + e +')'));
+  assert (typeof Symbol[e] === 'symbol');
+});
+
+var obj = {};
+Object.defineProperty(obj, a, { 'get' : function () {throw new ReferenceError ('foo'); } });
+Object.defineProperty(obj, b, { value : 5 });
+assert (obj[b] === 5);
+
+try {
+  obj[a];
+  assert (false);
+} catch (e) {
+  assert (e instanceof ReferenceError);
+  assert (e.message === 'foo');
+}
+
+var descriptor = Object.getOwnPropertyDescriptor(obj, b);
+
+assert (descriptor.configurable === false);
+assert (descriptor.enumerable === false);
+assert (descriptor.writable === false);
+assert (descriptor.value === 5);
+
+var foo = Symbol ('foo');
+assert (foo[Symbol.toStringTag] === 'Symbol');
+
+// Test same descriptions
+var symA = Symbol ('foobar');
+var symB = Symbol ('foobar');
+assert (symA !== symB);
+assert (symA != symB);
+
+var obj = { foobar : 55 };
+obj[symA] = 77;
+assert (obj["foobar"] !== obj[symA]);
+assert (obj["foobar"] != obj[symA]);