Ecma 6 script introduce block scope variables without hoisting. For example 

"use strict";
var y = {
        name: "Honza",
        age: 12
    };
console.log(y);             // { name: 'Honza', age: 12 }
if (true) {
    let y = "test";
    console.log(y);         // test
    for (let i = 0; i < 3; i++) {
        let y = i;
        console.log(y);     // 0 1 2
    }
    console.log(y);         // test
}

console.log(y);             // { name: 'Honza', age: 12 }

Currently we mark 'y' in every occurrence, but there three variables of y in the code. Should be marked only its scoped.