loops, closures and incorrect "this" value

[yernende]

If using declared in header of for-of loop variable in closure, placed in this loop, keyword "this" in that closure becomes equal to global object.

var servant = {
    sayNumbers() {
        for (let number of [1, 2, 3]) {
            (() => {
                number; //without number reference "this" is right
                console.log(this); //window
            })();
        }
    }
}
servant.sayNumbers();

This code is compiled into

var servant = {
    sayNumbers: function() {var S_ITER$0 = typeof Symbol!=='undefined'&&Symbol&&Symbol.iterator||'@@iterator';var S_MARK$0 = typeof Symbol!=='undefined'&&Symbol&&Symbol["__setObjectSetter__"];function GET_ITER$0(v){if(v){if(Array.isArray(v))return 0;var f;if(S_MARK$0)S_MARK$0(v);if(typeof v==='object'&&typeof (f=v[S_ITER$0])==='function'){if(S_MARK$0)S_MARK$0(void 0);return f.call(v);}if(S_MARK$0)S_MARK$0(void 0);if((v+'')==='[object Generator]')return v;}throw new Error(v+' is not iterable')};var $D$0;var $D$1;var $D$2;var $D$3;
        $D$3 = ([1, 2, 3]);$D$0 = GET_ITER$0($D$3);$D$2 = $D$0 === 0;$D$1 = ($D$2 ? $D$3.length : void 0);for (var number ;$D$2 ? ($D$0 < $D$1) : !($D$1 = $D$0["next"]())["done"];){number = ($D$2 ? $D$3[$D$0++] : $D$1["value"]);(function(number){var this$0 = this;
            (function()  {
                number;
                console.log(this$0); //window
            })();
        })(number);};$D$0 = $D$1 = $D$2 = $D$3 = void 0;
    }
}
servant.sayNumbers();

And all works fine if function, closing "number" variable, is called via "call" method with definition of "this".