v8/test/mjsunit/regress/regress-3650-3.js

// Copyright 2016 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: --allow-natives-syntax --opt

function foo(a) {
  for (var d in a) {
    delete a[1];
  }
}

%PrepareFunctionForOptimization(foo);
foo([1,2,3]);
foo([2,3,4]);
%OptimizeFunctionOnNextCall(foo);
foo([1,2,3]);
assertOptimized(foo);