[ESnext] Implement Object spread

test/mjsunit/harmony/object-spread-basic.js

+// Copyright 2016 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-object-spread
+
+var x = {a: 1};
+var y = { ...x};
+assertEquals(x, y);
+
+assertEquals({}, y = { ...{} } );
+assertEquals({}, y = { ...undefined });
+assertEquals({}, y = { ...null });
+
+assertEquals({}, y = { ...1 });
+assertEquals({0: 'f', 1: 'o', 2: 'o'}, y = { ...'foo' });
+assertEquals({0: 0, 1: 1}, y = { ...[0, 1] });
+assertEquals({}, { ...new Proxy({}, {}) });
+
+assertEquals({a: 2}, y = { ...x, a: 2 });
+assertEquals({a: 1, b: 1}, y = { ...x, b: 1 });
+assertEquals({a: 1}, y = { a: 2, ...x });
+assertEquals({a: 1, b: 1}, y = { a:2, ...x, b: 1 });
+assertEquals({a: 3}, y = { a: 2, ...x, a: 3 });
+
+var z = { b: 1}
+assertEquals({a: 1, b: 1}, y = { ...x, ...z });
+assertEquals({a: 1, b: 1}, y = { a: 2, ...x, ...z });
+assertEquals({a: 1, b: 1}, y = { b: 2, ...z, ...x });
+assertEquals({a: 1, b: 1}, y = { a: 1, ...x, b: 2, ...z });
+assertEquals({a: 1, b: 2}, y = { a: 1, ...x, ...z, b: 2 });
+assertEquals({a: 2, b: 2}, y = { ...x, ...z, a:2, b: 2 });
+
+var x = {}
+Object.defineProperty(x, 'a', {
+  enumerable: false,
+  configurable: false,
+  writable: false,
+  value: 1
+});
+assertEquals({}, { ...x });
+
+var x = {}
+Object.defineProperty(x, 'a', {
+  enumerable: true,
+  configurable: false,
+  writable: false,
+  value: 1
+});
+var y = { ...x };
+var prop = Object.getOwnPropertyDescriptor(y, 'a');
+assertEquals(prop.value, 1);
+assertTrue(prop.enumerable);
+assertTrue(prop.configurable);
+assertTrue(prop.writable);
+
+var x = { __proto__: z }
+assertEquals({}, { ...x });
+
+var x = {
+  get a() { return 1; },
+  set a(_) { assertUnreachable("setter called"); },
+};
+assertEquals({ a: 1 }, y = { ...x });
+
+var x = {
+  method() { return 1; },
+};
+assertEquals(x, y = { ...x });
+
+var x = {
+  *gen() { return {value: 1, done: true} ; },
+};
+assertEquals(x, y = { ...x });
+
+var x = {
+  get a() { throw new Error(); },
+};
+assertThrows(() => { y = { ...x } });
+
+var p = new Proxy({}, {
+  ownKeys() { throw new Error(); }
+});
+assertThrows(() => { y = { ...p } });
+
+var p = new Proxy({}, {
+  ownKeys() { [1]; },
+  get() { throw new Error(); }
+});
+assertThrows(() => { y = { ...p } });
+
+var p = new Proxy({}, {
+  ownKeys() { [1]; },
+  getOwnPropertyDescriptor() { throw new Error(); }
+});
+assertThrows(() => { y = { ...p } });
+
+var p = new Proxy(z, {
+  ownKeys() { return Object.keys(z); },
+  get(_, prop) { return z[prop]; },
+  getOwnPropertyDescriptor(_, prop) {
+    return Object.getOwnPropertyDescriptor(z, prop);
+  },
+});
+assertEquals(z, y = { ...p });
+
+var x = { a:1 };
+assertEquals(x, y = { set a(_) { throw new Error(); }, ...x });
+
+var x = { a:1 };
+assertEquals(x, y = { get a() { throw new Error(); }, ...x });