[runtime] Throw if re-declaring a non-configurable accessor.

If an accessor property is non-configurable, one should not be able
to re-declare it as a function. This specifically applies to special properties like window.location.

BUG=chromium:670596

Review-Url: https://codereview.chromium.org/2582493002
Cr-Commit-Position: refs/heads/master@{#41725}

src/runtime/runtime-scopes.cc

@@ -88,8 +88,7 @@ Object* DeclareGlobal(
       // function.
       PropertyDetails old_details = it.property_details();
       if (old_details.IsReadOnly() || old_details.IsDontEnum() ||
-          (it.state() == LookupIterator::ACCESSOR &&
-           it.GetAccessors()->IsAccessorPair())) {
+          (it.state() == LookupIterator::ACCESSOR)) {
         // ECMA-262 section 15.1.11 GlobalDeclarationInstantiation 5.d:
         // If hasRestrictedGlobal is true, throw a SyntaxError exception.
         // ECMA-262 section 18.2.1.3 EvalDeclarationInstantiation 8.a.iv.1.b:

test/cctest/test-api-accessors.cc

@@ -247,3 +247,33 @@ TEST(CachedAccessorCrankshaft) {
 
   ExpectInt32("g()", 789);
 }
+
+namespace {
+
+static void Setter(v8::Local<v8::String> name, v8::Local<v8::Value> value,
+                   const v8::PropertyCallbackInfo<void>& info) {}
+}
+
+// Re-declaration of non-configurable accessors should throw.
+TEST(RedeclareAccessor) {
+  v8::HandleScope scope(CcTest::isolate());
+  LocalContext env;
+
+  v8::Local<v8::FunctionTemplate> templ =
+      v8::FunctionTemplate::New(CcTest::isolate());
+
+  v8::Local<v8::ObjectTemplate> object_template = templ->InstanceTemplate();
+  object_template->SetAccessor(
+      v8_str("foo"), NULL, Setter, v8::Local<v8::Value>(),
+      v8::AccessControl::DEFAULT, v8::PropertyAttribute::DontDelete);
+
+  v8::Local<v8::Context> ctx =
+      v8::Context::New(CcTest::isolate(), nullptr, object_template);
+
+  // Declare function.
+  v8::Local<v8::String> code = v8_str("function foo() {};");
+
+  v8::TryCatch try_catch(CcTest::isolate());
+  v8::Script::Compile(ctx, code).ToLocalChecked()->Run(ctx).IsEmpty();
+  CHECK(try_catch.HasCaught());
+}