[es7] implement |do| expressions proposal

test/mjsunit/harmony/do-expressions.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-do-expressions --harmony-sloppy-let --allow-natives-syntax
+
+function returnValue(v) { return v; }
+function MyError() {}
+
+function TestBasic() {
+  // Looping and lexical declarations
+  assertEquals(512, returnValue(do {
+    let n = 2;
+    for (let i = 0; i < 4; i++) n <<= 2;
+  }));
+
+  // Strings do the right thing
+  assertEquals("spooky halloween", returnValue(do {
+    "happy halloween".replace('happy', 'spooky');
+  }));
+
+  // Do expressions with no completion produce an undefined value
+  assertEquals(undefined, returnValue(do {}));
+  assertEquals(undefined, returnValue(do { var x = 99; }));
+  assertEquals(undefined, returnValue(do { function f() {}; }));
+  assertEquals(undefined, returnValue(do { let z = 33; }));
+
+  // Propagation of exception
+  assertThrows(function() {
+    (do {
+      throw new MyError();
+      "potatoes";
+    });
+  }, MyError);
+
+  // Real-world use case for desugaring
+  var array = [1, 2, 3, 4, 5], iterable = [6, 7, 8,9];
+  assertEquals([1, 2, 3, 4, 5, 6, 7, 8, 9], do {
+    for (var element of iterable) array.push(element);
+    array;
+  });
+
+  // Nested do-expressions
+  assertEquals(125, do { (do { (do { 5 * 5 * 5 }) }) });
+
+  // Directives are not honoured
+  (do {
+    "use strict";
+    foo = 80;
+    assertEquals(foo, 80);
+  });
+
+  // Non-empty operand stack testing
+  var O = {
+    method1() {
+      let x = 256;
+      return x + do {
+        for (var i = 0; i < 4; ++i) x += i;
+      } + 17;
+    },
+    method2() {
+      let x = 256;
+      this.reset();
+      return x + do {
+        for (var i = 0; i < this.length(); ++i) x += this.index() * 2;
+      };
+    },
+    _index: 0,
+    index() {
+      return ++this._index;
+    },
+    _length: 4,
+    length() { return this._length; },
+    reset() { this._index = 0; }
+  };
+  assertEquals(535, O["method" + do { 1 } + ""]());
+  assertEquals(532, O["method" + do { ({ valueOf() { return "2"; } }); }]());
+  assertEquals(532, O[
+      do { let s = ""; for (let c of "method") s += c; } + "2"]());
+}
+TestBasic();
+
+
+function TestDeoptimization1() {
+  function f(v) {
+    return 88 + do {
+      v.a * v.b + v.c;
+    };
+  }
+
+  var o1 = {};
+  o1.a = 10;
+  o1.b = 5;
+  o1.c = 50;
+
+  var o2 = {};
+  o2.c = 100;
+  o2.a = 10;
+  o2.b = 10;
+
+  assertEquals(188, f(o1));
+  assertEquals(188, f(o1));
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals(188, f(o1));
+  assertOptimized(f);
+  assertEquals(288, f(o2));
+  assertUnoptimized(f);
+  assertEquals(288, f(o2));
+}
+TestDeoptimization1();