function assert(b) {
    if (!b)
        throw new Error("Bad assertion.")
}
noInline(assert);

let objs = [
    {f: 50},
    {f: 50, g: 70},
    {g: 50, f: 70},
    {h: 50, f: 70},
    {z: 50, f: 70},
    {k: 50, f: 70},
];

let s1 = Symbol();
let s2 = Symbol();
for (let o of objs)
    o[s1] = "foo";

function foo(o) {
    assert(o.hasOwnProperty("f"));
    assert(!o.hasOwnProperty("ff"));
    assert(o.hasOwnProperty(s1));
    assert(!o.hasOwnProperty(s2));
}
noInline(foo);

for (let i = 0; i < 40000; ++i) {
    foo(objs[i % objs.length]);
}