Correctly report error in for-in start in case of proxies (#4165)

In case of Proxies the "ownKeys" call can return an incompatible
value for a for-in statement. In such cases the error should be
propagated to the user.

Fixes: #4159

JerryScript-DCO-1.0-Signed-off-by: Peter Gal pgal.usz@partner.samsung.com

tests/jerry/es.next/proxy-for-in.js

@@ -0,0 +1,78 @@
+// 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.
+
+// 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.
+
+var handlerBoolean = {
+  ownKeys: function() { return true; },
+}
+var boolProxy = new Proxy({}, handlerBoolean);
+
+try {
+  for (var a in boolProxy) {
+    // This should never be called.
+    assert (false);
+  }
+
+  assert (false);
+} catch (ex) {
+  assert (ex instanceof TypeError);
+}
+
+
+var handlerSymbol = {
+  ownKeys: function() { return Symbol("alma"); },
+}
+var symbolProxy = new Proxy({}, handlerSymbol);
+
+try {
+  for (var a in symbolProxy) {
+    // This should never be called.
+    assert (false);
+  }
+
+  assert (false);
+} catch (ex) {
+  assert (ex instanceof TypeError);
+}
+
+
+var handlerNumber = {
+  ownKeys: function() { return 1; },
+}
+var numberProxy = new Proxy({}, handlerNumber);
+
+try {
+  for (var a in numberProxy) {
+    // This should never be called.
+    assert (false);
+  }
+
+  assert (false);
+} catch (ex) {
+  assert (ex instanceof TypeError);
+}
+
+
+var handlerObject = {
+  ownKeys: function() { return {}; },
+}
+var objectProxy = new Proxy({}, handlerObject);
+
+for (var a in objectProxy) {
+  // This should never be called.
+  assert (false);
+}

tests/test262-es6-excludelist.xml

@@ -56,7 +56,6 @@
   <test id="built-ins/Proxy/enumerate/result-not-an-object-throws-string.js"><reason>For-in supports proxy</reason></test>
   <test id="built-ins/Proxy/enumerate/result-not-an-object-throws-symbol.js"><reason>For-in supports proxy</reason></test>
   <test id="built-ins/Proxy/enumerate/result-not-an-object-throws-undefined.js"><reason>For-in supports proxy</reason></test>
-  <test id="built-ins/Proxy/enumerate/null-handler.js"><reason>For-in supports proxy</reason></test>
   <test id="built-ins/Proxy/enumerate/return-trap-result.js"><reason></reason></test>
   <test id="built-ins/Proxy/enumerate/return-trap-result-no-value.js"><reason></reason></test>
   <test id="built-ins/Proxy/enumerate/trap-is-not-callable.js"><reason>For-in supports proxy</reason></test>