arrow lexical bind arguments

test.js

var af = function (x, y) {
    let arr;
    if (false) {
        let arguments = 0;
        arr = () => arguments;
    } else {
        let arguments = 1;
        arr = () => arguments;
    }
    return arr;
}

var val = af(10, 12);
debug(val() === 1);