function test() {

// Array.from -> Set -> [[Set]]
var set = [];
var p = new Proxy({}, { set: function(o, k, v) { set.push(k); o[k] = v; return true; }});
Array.from.call(function(){ return p; }, {length:2, 0:1, 1:2});
return set + '' === "length";
      
}

if (!test())
    throw new Error("Test failed");