[es6] Implement destructuring binding in try/catch

test/mjsunit/harmony/destructuring.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-destructuring
 // Flags: --harmony-default-parameters --harmony-rest-parameters
 
 (function TestObjectLiteralPattern() {
   var { x : x, y : y, get, set } = { x : 1, y : 2, get: 3, set: 4 };
   assertEquals(1, x);
@@ skipping 1089 matching lines @@
 
 (function TestLegacyConstDestructuringInForLoop() {
   var result;
   for (const {foo} of [{foo: 1}]) { result = foo; }
   assertEquals(1, result);
 })();
 
 (function TestDestructuringArrayWithoutInitializer() {
   assertThrows('var [foo]', TypeError);
 })();
+
+
+(function TestCatch() {
+  "use strict";
+
+  try {
+    throw {foo: 1, bar: 2};
+  } catch ({foo, bar, baz = 3}) {
+    assertEquals(1, foo);
+    assertEquals(2, bar);
+    assertEquals(3, baz);
+  }
+
+  try {
+    throw [1, 2, 3];
+  } catch ([foo, ...bar]) {
+    assertEquals(1, foo);
+    assertEquals([2, 3], bar);
+  }
+
+  // Should be lexically scoped inside catch scopes.
+  assertEquals("undefined", typeof foo);

[rossberg, 2015/11/03 12:00:50]

This is not a sufficient test, because it will be true even if the variable _is_
scoped here but uninitialised. Perhaps add a test that shadows a variable in
this scope and check that its value isn't clobbered.

[adamk, 2015/11/03 20:35:20]

Fixed.

Not sure how much more to test here, I'm not doing anything special to support
catch.

[rossberg, 2015/11/04 10:26:56]

Yeah, I think it's fine. Setting up the descriptor properly (esp the scopes) is
the main thing that could go wrong.

+  assertEquals("undefined", typeof bar);
+  assertEquals("undefined", typeof baz);
+})();