Ensure slow properties for simple {__proto__:null} literals.

test/mjsunit/object-literal.js

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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@@ skipping 242 matching lines @@
   set 5E0(_) {},
   set 6e-0(_) {},
   set 7E-0(_) {},
   set 0x8(_) {},
   set 0X9(_) {},
 });
 TestNumericNamesSetter(['1.2', '1.3'], {
   set 1.2(_) {; },
   set 1.30(_) {; }
 });
+
+
+(function TestLiteralWithNullProto() {
+  // Assume dictionary usage for simple null prototype literal objects,
+  // this is equivalent to Object.create(null).
+  var obj = {__proto__:null};
+  assertFalse(%HasFastProperties(obj));

[adamk, 2016/10/25 11:14:24]

You'll need --allow-natives-syntax in Flags

[Camillo Bruni, 2017/03/13 17:21:44]

arg, bitten by my own smart aliases that add these flags automatically :P

+  assertEquals(Object.getPrototypeOf(obj), null);
+  // Once we add inline properties we probably don't want slow properties
+  // anymore.
+  var obj2 = {__proto__:null, a:1, b:2};

[adamk, 2016/10/25 11:14:24]

Please add a test with computed properties and non-compile-time-values, e.g.

obj3 = {__proto__: null, ["a"]: 1}

obj4 = {__proto__: null, a: obj3}

[Camillo Bruni, 2017/03/13 17:21:44]

done.

+  assertTrue(%HasFastProperties(obj2));
+  assertEquals(Object.getPrototypeOf(obj2), null);
+
+})()