Implement subclassing Arrays.

test/mjsunit/harmony/classes-subclass-arrays.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-classes
+'use strict';
+
+(function TestDefaultConstructor() {
+  class Stack extends Array { }
+  {
+    let s1 = new Stack();
+    assertSame(Stack.prototype, s1.__proto__);
+    assertTrue(Array.isArray(s1));
+    assertSame(0, s1.length);
+    s1[0] = 'xyz';
+    assertSame(1, s1.length);
+    assertSame('xyz', s1[0]);
+    s1.push(42);
+    assertSame(2, s1.length);
+    assertSame('xyz', s1[0]);
+    assertSame(42, s1[1]);
+  }
+
+  {
+    let s2 = new Stack(10);
+    assertSame(Stack.prototype, s2.__proto__);
+    assertTrue(Array.isArray(s2));
+    assertSame(10, s2.length);
+    assertSame(undefined, s2[0]);
+  }
+
+  {
+    let a = [1,2,3];
+    let s3 = new Stack(a);
+    assertSame(Stack.prototype, s3.__proto__);
+    assertTrue(Array.isArray(s3));
+    assertSame(1, s3.length);
+    assertSame(a, s3[0]);
+  }
+
+  {
+    let s4 = new Stack(1, 2, 3);
+    assertSame(Stack.prototype, s4.__proto__);
+    assertTrue(Array.isArray(s4));
+    assertSame(3, s4.length);
+    assertSame(1, s4[0]);
+    assertSame(2, s4[1]);
+    assertSame(3, s4[2]);
+  }
+
+  {
+    let s5 = new Stack(undefined, undefined, undefined);
+    assertSame(Stack.prototype, s5.__proto__);
+    assertTrue(Array.isArray(s5));
+    assertSame(3, s5.length);
+    assertSame(undefined, s5[0]);
+    assertSame(undefined, s5[1]);
+    assertSame(undefined, s5[2]);
+  }
+}());
+
+
+(function TestEmptyArgsSuper() {
+  class Stack extends Array {
+    constructor() { super(); }
+  }
+  let s1 = new Stack();
+  assertSame(Stack.prototype, s1.__proto__);
+  assertTrue(Array.isArray(s1));
+  assertSame(0, s1.length);
+  s1[0] = 'xyz';
+  assertSame(1, s1.length);
+  assertSame('xyz', s1[0]);
+  s1.push(42);
+  assertSame(2, s1.length);
+  assertSame('xyz', s1[0]);
+  assertSame(42, s1[1]);
+}());
+
+
+(function TestOneArgSuper() {
+  class Stack extends Array {
+    constructor(x) {
+      super(x);
+    }
+  }
+
+  {
+    let s2 = new Stack(10, 'ignored arg');
+    assertSame(Stack.prototype, s2.__proto__);
+    assertTrue(Array.isArray(s2));
+    assertSame(10, s2.length);
+    assertSame(undefined, s2[0]);
+  }
+
+  {
+    let a = [1,2,3];
+    let s3 = new Stack(a, 'ignored arg');
+    assertSame(Stack.prototype, s3.__proto__);
+    assertTrue(Array.isArray(s3));
+    assertSame(1, s3.length);
+    assertSame(a, s3[0]);
+  }
+}());
+
+
+(function TestMultipleArgsSuper() {
+  class Stack extends Array {
+    constructor(x, y, z) {
+      super(x, y, z);
+    }
+  }
+  {
+    let s4 = new Stack(1, 2, 3, 4, 5);
+    assertSame(Stack.prototype, s4.__proto__);
+    assertTrue(Array.isArray(s4));
+    assertSame(3, s4.length);
+    assertSame(1, s4[0]);
+    assertSame(2, s4[1]);
+    assertSame(3, s4[2]);
+  }
+
+  {
+    let s5 = new Stack(undefined);
+    assertSame(Stack.prototype, s5.__proto__);
+    assertTrue(Array.isArray(s5));
+    assertTrue(s5.__proto__ == Stack.prototype);
+    assertSame(3, s5.length);
+    assertSame(undefined, s5[0]);
+    assertSame(undefined, s5[1]);
+    assertSame(undefined, s5[2]);
+  }
+}());
+
+
+(function TestArrayConcat() {
+  class Stack extends Array { }
+  let s1 = new Stack(1,2,3);
+
+  assertArrayEquals([1,2,3,4,5,6], s1.concat([4,5,6]));
+  assertArrayEquals([4,5,6,1,2,3], [4,5,6].concat(s1));
+}());
+
+
+(function TestJSONStringify() {
+  class Stack extends Array { }
+
+  let s1 = new Stack(1,2,3);
+  assertSame("[1,2,3]", JSON.stringify(s1));
+}());